Java by API/java.lang/Class
Содержание
- 1 Class: Annotation[] getAnnotations()
- 2 Class: forName(String classDec)
- 3 Class: getCanonicalName()
- 4 Class: getClasses()
- 5 Class: getComponentType()
- 6 Class: getConstructor(Class<?>...)
- 7 Class: getConstructors()
- 8 Class: getDeclaredConstructors()
- 9 Class: getDeclaredFields()
- 10 Class: getDeclaredMethods()
- 11 Class: getDeclaredMethod(String name, Class<?>... parameterTypes)
- 12 Class: getDeclaringClass()
- 13 Class: getEnumConstants()
- 14 Class: getFields()
- 15 Class: getGenericInterfaces()
- 16 Class: getGenericSuperclass()
- 17 Class: getInterfaces()
- 18 Class: getMethods()
- 19 Class: getModifiers()
- 20 Class: getName()
- 21 Class: getPackage()
- 22 Class: getProtectionDomain()
- 23 Class: getResourceAsStream(String name)
- 24 Class: getResource(String name) (absolute from the classpath)
- 25 Class: getResource(String name) (relative to the class location)
- 26 Class: getSuperclass()
- 27 Class: getTypeParameters()
- 28 Class: isArray()
- 29 Class: isAssignableFrom(Class<?> cls)
- 30 Class: isEnum()
- 31 Class: isInstance(Object obj)
- 32 Class: isInterface()
- 33 Class: Method getMethod(String name, Class<?>... parameterTypes)
- 34 Class: newInstance()
Class: Annotation[] getAnnotations()
<source lang="java">
import java.lang.annotation.Annotation; import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; @Retention(RetentionPolicy.RUNTIME) @interface MyAnnotation {
String stringValue(); int intValue();
} @Retention(RetentionPolicy.RUNTIME) @interface What {
String description();
} @What(description = "An annotation test class") @MyAnnotation(stringValue = "for class", intValue = 100) public class Main {
@What(description = "An annotation test method")
@MyAnnotation(stringValue = "Annotation Example", intValue = 100)
public static void myMethod(String str, int i) {
}
public static void main(String[] arg) throws Exception {
Main ob = new Main();
Annotation[] annos = ob.getClass().getAnnotations();
System.out.println("All annotations for Meta2:");
for (Annotation a : annos)
System.out.println(a);
}
}
</source>
Class: forName(String classDec)
<source lang="java">
/*
* Output:
Constructors:
public java.awt.Dimension(java.awt.Dimension) public java.awt.Dimension(int,int) public java.awt.Dimension()
Fields:
public int java.awt.Dimension.width public int java.awt.Dimension.height
Methods:
public int java.awt.Dimension.hashCode() public boolean java.awt.Dimension.equals(java.lang.Object) public java.lang.String java.awt.Dimension.toString() public java.awt.Dimension java.awt.Dimension.getSize() public void java.awt.Dimension.setSize(int,int) public void java.awt.Dimension.setSize(double,double) public void java.awt.Dimension.setSize(java.awt.Dimension) public double java.awt.Dimension.getHeight() public double java.awt.Dimension.getWidth() public java.lang.Object java.awt.geom.Dimension2D.clone() public void java.awt.geom.Dimension2D.setSize(java.awt.geom.Dimension2D) public final native java.lang.Class java.lang.Object.getClass() public final void java.lang.Object.wait() throws java.lang.InterruptedException public final void java.lang.Object.wait(long,int) throws java.lang.InterruptedException public final native void java.lang.Object.wait(long) throws java.lang.InterruptedException public final native void java.lang.Object.notify() public final native void java.lang.Object.notifyAll() * */
import java.lang.reflect.Constructor; import java.lang.reflect.Field; import java.lang.reflect.Method; public class MainClass {
public static void main(String args[]) {
try {
Class c = Class.forName("java.awt.Dimension");
System.out.println("Constructors:");
Constructor constructors[] = c.getConstructors();
for (int i = 0; i < constructors.length; i++) {
System.out.println(" " + constructors[i]);
}
System.out.println("Fields:");
Field fields[] = c.getFields();
for (int i = 0; i < fields.length; i++) {
System.out.println(" " + fields[i]);
}
System.out.println("Methods:");
Method methods[] = c.getMethods();
for (int i = 0; i < methods.length; i++) {
System.out.println(" " + methods[i]);
}
} catch (Exception e) {
System.out.println("Exception: " + e);
}
}
}
</source>
Class: getCanonicalName()
<source lang="java">
/*
* Copyright (c) 1995 - 2008 Sun Microsystems, Inc. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * - Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * - Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * - Neither the name of Sun Microsystems nor the names of its * contributors may be used to endorse or promote products derived * from this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */
import static java.lang.System.out; import java.lang.annotation.Annotation; import java.lang.reflect.Modifier; import java.lang.reflect.Type; import java.lang.reflect.TypeVariable; import java.util.ArrayList; import java.util.List; public class Main {
public static void main(String... args) {
try {
Class<?> c = Class.forName(args[0]);
out.format("Class:%n %s%n%n", c.getCanonicalName());
out.format("Modifiers:%n %s%n%n", Modifier.toString(c.getModifiers()));
out.format("Type Parameters:%n");
TypeVariable[] tv = c.getTypeParameters();
if (tv.length != 0) {
out.format(" ");
for (TypeVariable t : tv)
out.format("%s ", t.getName());
out.format("%n%n");
} else {
out.format(" -- No Type Parameters --%n%n");
}
out.format("Implemented Interfaces:%n");
Type[] intfs = c.getGenericInterfaces();
if (intfs.length != 0) {
for (Type intf : intfs)
out.format(" %s%n", intf.toString());
out.format("%n");
} else {
out.format(" -- No Implemented Interfaces --%n%n");
}
out.format("Inheritance Path:%n");
List<Class> l = new ArrayList<Class>();
printAncestor(c, l);
if (l.size() != 0) {
for (Class<?> cl : l)
out.format(" %s%n", cl.getCanonicalName());
out.format("%n");
} else {
out.format(" -- No Super Classes --%n%n");
}
out.format("Annotations:%n");
Annotation[] ann = c.getAnnotations();
if (ann.length != 0) {
for (Annotation a : ann)
out.format(" %s%n", a.toString());
out.format("%n");
} else {
out.format(" -- No Annotations --%n%n");
}
// production code should handle this exception more gracefully
} catch (ClassNotFoundException x) {
x.printStackTrace();
}
}
private static void printAncestor(Class<?> c, List<Class> l) {
Class<?> ancestor = c.getSuperclass();
if (ancestor != null) {
l.add(ancestor);
printAncestor(ancestor, l);
}
}
}
</source>
Class: getClasses()
<source lang="java">
import java.util.Arrays; import javax.swing.JTable; public class Main {
public static void main(final String[] args) {
printMemberClasses(JTable.class);
}
public static void printMemberClasses(final Class dataType) {
final Class[] nestedClasses = dataType.getClasses();
final Class[] declaredNestedClasses = dataType.getDeclaredClasses();
final Class[] nestedInterfaces = dataType.getInterfaces();
final Class declaringClass = dataType.getDeclaringClass();
System.out.println("Member Class infor for: " + dataType.getName());
System.out.println("Nested Classes: " + Arrays.asList(nestedClasses));
System.out.println("Declared Nested Classes: " + Arrays.asList(declaredNestedClasses));
System.out.println("Interfaces: " + Arrays.asList(nestedInterfaces));
System.out.println("Declaring Class: " + declaringClass);
}
}
</source>
Class: getComponentType()
<source lang="java">
/*
Output:
Array of: int Array size: 3
* */
import java.lang.reflect.Array; public class MainClass {
public static void main (String args[]) {
Object array = Array.newInstance(int.class, 3);
Class type = array.getClass();
if (type.isArray()) {
Class elementType = type.getComponentType();
System.out.println("Array of: " + elementType);
System.out.println("Array size: " + Array.getLength(array));
}
}
}
</source>
Class: getConstructor(Class<?>...)
<source lang="java">
import java.lang.reflect.Constructor; public class Main {
public static void main(String[] args) {
Constructor[] cs = String.class.getConstructors();
for (int i = 0; i < cs.length; i++) {
System.out.println(cs[i]);
}
try {
Constructor c = String.class.getConstructor(new Class[] { String.class });
System.out.println(c);
} catch (SecurityException e) {
e.printStackTrace();
} catch (NoSuchMethodException e) {
e.printStackTrace();
}
}
}
</source>
Class: getConstructors()
<source lang="java">
/*
* Output:
Constructors:
public java.awt.Dimension(java.awt.Dimension) public java.awt.Dimension(int,int) public java.awt.Dimension()
Fields:
public int java.awt.Dimension.width public int java.awt.Dimension.height
Methods:
public int java.awt.Dimension.hashCode() public boolean java.awt.Dimension.equals(java.lang.Object) public java.lang.String java.awt.Dimension.toString() public java.awt.Dimension java.awt.Dimension.getSize() public void java.awt.Dimension.setSize(int,int) public void java.awt.Dimension.setSize(double,double) public void java.awt.Dimension.setSize(java.awt.Dimension) public double java.awt.Dimension.getHeight() public double java.awt.Dimension.getWidth() public java.lang.Object java.awt.geom.Dimension2D.clone() public void java.awt.geom.Dimension2D.setSize(java.awt.geom.Dimension2D) public final native java.lang.Class java.lang.Object.getClass() public final void java.lang.Object.wait() throws java.lang.InterruptedException public final void java.lang.Object.wait(long,int) throws java.lang.InterruptedException public final native void java.lang.Object.wait(long) throws java.lang.InterruptedException public final native void java.lang.Object.notify() public final native void java.lang.Object.notifyAll() * */
import java.lang.reflect.Constructor; import java.lang.reflect.Field; import java.lang.reflect.Method; public class MainClass {
public static void main(String args[]) {
try {
Class c = Class.forName("java.awt.Dimension");
System.out.println("Constructors:");
Constructor constructors[] = c.getConstructors();
for (int i = 0; i < constructors.length; i++) {
System.out.println(" " + constructors[i]);
}
System.out.println("Fields:");
Field fields[] = c.getFields();
for (int i = 0; i < fields.length; i++) {
System.out.println(" " + fields[i]);
}
System.out.println("Methods:");
Method methods[] = c.getMethods();
for (int i = 0; i < methods.length; i++) {
System.out.println(" " + methods[i]);
}
} catch (Exception e) {
System.out.println("Exception: " + e);
}
}
}
</source>
Class: getDeclaredConstructors()
<source lang="java">
/* java.util.ArrayList: java.util.ArrayList: Collection java.util.ArrayList: int
*/
import java.lang.reflect.Constructor; public class MainClass {
public static void main(String[] args) {
try {
Class c = Class.forName("java.util.ArrayList");
Constructor constructors[] = c.getDeclaredConstructors();
for (int i = 0; i < constructors.length; i++) {
System.out.print(constructors[i].getName() + ": ");
Class parameters[];
parameters = constructors[i].getParameterTypes();
for (int j = 0; j < parameters.length; j++) {
String s = parameters[j].getName();
s = s.substring(s.lastIndexOf(".") + 1, s.length());
System.out.print(s + " ");
}
System.out.println("");
}
} catch (Exception ex) {
ex.printStackTrace();
}
}
}
</source>
Class: getDeclaredFields()
<source lang="java">
/* ArrayList, serialVersionUID, long, private static final ArrayList, elementData, [Ljava.lang.Object;, private transient ArrayList, size, int, private Arrays, INSERTIONSORT_THRESHOLD, int, private static final BitSet, ADDRESS_BITS_PER_UNIT, int, private static final BitSet, BITS_PER_UNIT, int, private static final BitSet, BIT_INDEX_MASK, int, private static final BitSet, WORD_MASK, long, private static final BitSet, bits, [J, private BitSet, unitsInUse, int, private transient BitSet, serialVersionUID, long, private static final BitSet, trailingZeroTable, [B, private static final Collections, BINARYSEARCH_THRESHOLD, int, private static final Collections, REVERSE_THRESHOLD, int, private static final Collections, SHUFFLE_THRESHOLD, int, private static final Collections, FILL_THRESHOLD, int, private static final Collections, ROTATE_THRESHOLD, int, private static final Collections, COPY_THRESHOLD, int, private static final Collections, REPLACEALL_THRESHOLD, int, private static final Collections, INDEXOFSUBLIST_THRESHOLD, int, private static final Collections, r, java.util.Random, private static Collections, EMPTY_SET, java.util.Set, public static final Collections, EMPTY_LIST, java.util.List, public static final Collections, EMPTY_MAP, java.util.Map, public static final Collections, REVERSE_ORDER, java.util.ruparator, private static final HashMap, DEFAULT_INITIAL_CAPACITY, int, static final HashMap, MAXIMUM_CAPACITY, int, static final HashMap, DEFAULT_LOAD_FACTOR, float, static final HashMap, table, [Ljava.util.HashMap$Entry;, transient HashMap, size, int, transient HashMap, threshold, int, HashMap, loadFactor, float, final HashMap, modCount, int, transient volatile HashMap, NULL_KEY, java.lang.Object, static final HashMap, entrySet, java.util.Set, private transient HashMap, serialVersionUID, long, private static final HashSet, serialVersionUID, long, static final HashSet, map, java.util.HashMap, private transient HashSet, PRESENT, java.lang.Object, private static final WeakHashMap, DEFAULT_INITIAL_CAPACITY, int, private static final WeakHashMap, MAXIMUM_CAPACITY, int, private static final WeakHashMap, DEFAULT_LOAD_FACTOR, float, private static final WeakHashMap, table, [Ljava.util.WeakHashMap$Entry;, private WeakHashMap, size, int, private WeakHashMap, threshold, int, private WeakHashMap, loadFactor, float, private final WeakHashMap, queue, java.lang.ref.ReferenceQueue, private final WeakHashMap, modCount, int, private volatile WeakHashMap, NULL_KEY, java.lang.Object, private static final WeakHashMap, entrySet, java.util.Set, private transient
* **/
import java.lang.reflect.Field; import java.lang.reflect.Modifier; public class MainClass {
public static void main(String args[]) throws Exception {
String names[] = { "ArrayList", "Arrays", "BitSet", "Collection", "Collections", "Dictionary",
"Enumeration", "HashMap", "HashSet", "WeakHashMap" };
for (int i = 0, n = names.length; i < n; i++) {
String className = "java.util." + names[i];
Class theClass = Class.forName(className);
Field fields[] = theClass.getDeclaredFields();
for (int j = 0, m = fields.length; j < m; j++) {
System.out.println(names[i] + ", " + fields[j].getName() + ", "
+ fields[j].getType().getName() + ", " + Modifier.toString(fields[j].getModifiers()));
}
}
}
}
</source>
Class: getDeclaredMethods()
<source lang="java">
/*
* Output:
Public Methods:
a1 a2 * */
import java.lang.reflect.Method; import java.lang.reflect.Modifier; public class MainClass {
public static void main(String args[]) {
try {
MyClass a = new MyClass();
Class c = a.getClass();
System.out.println("Public Methods:");
Method methods[] = c.getDeclaredMethods();
for (int i = 0; i < methods.length; i++) {
int modifiers = methods[i].getModifiers();
if (Modifier.isPublic(modifiers)) {
System.out.println(" " + methods[i].getName());
}
}
} catch (Exception e) {
System.out.println("Exception: " + e);
}
}
} class MyClass {
public void a1() {
}
public void a2() {
}
protected void a3() {
}
private void a4() {
}
}
</source>
Class: getDeclaredMethod(String name, Class<?>... parameterTypes)
<source lang="java">
import java.io.PrintStream; import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; public class Main {
public static void main(String[] args) throws NoSuchMethodException,
IllegalAccessException, InvocationTargetException {
Method m = PrintStream.class.getDeclaredMethod("println", String.class);
m.invoke(System.out, "Hello, World!");
}
}
</source>
Class: getDeclaringClass()
<source lang="java">
import java.util.Arrays; import javax.swing.JTable; public class Main {
public static void main(final String[] args) {
printMemberClasses(JTable.class);
}
public static void printMemberClasses(final Class dataType) {
final Class[] nestedClasses = dataType.getClasses();
final Class[] declaredNestedClasses = dataType.getDeclaredClasses();
final Class[] nestedInterfaces = dataType.getInterfaces();
final Class declaringClass = dataType.getDeclaringClass();
System.out.println("Member Class infor for: " + dataType.getName());
System.out.println("Nested Classes: " + Arrays.asList(nestedClasses));
System.out.println("Declared Nested Classes: " + Arrays.asList(declaredNestedClasses));
System.out.println("Interfaces: " + Arrays.asList(nestedInterfaces));
System.out.println("Declaring Class: " + declaringClass);
}
}
</source>
Class: getEnumConstants()
<source lang="java">
/*
* Copyright (c) 1995 - 2008 Sun Microsystems, Inc. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * - Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * - Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * - Neither the name of Sun Microsystems nor the names of its * contributors may be used to endorse or promote products derived * from this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */
import static java.lang.System.out; import java.util.Arrays; enum Eon {
HADEAN, ARCHAEAN, PROTEROZOIC, PHANEROZOIC
} public class Main {
public static void main(String... args) {
try {
Class<?> c = (args.length == 0 ? Eon.class : Class.forName(args[0]));
out.format("Enum name: %s%nEnum constants: %s%n", c.getName(), Arrays
.asList(c.getEnumConstants()));
if (c == Eon.class)
out.format(" Eon.values(): %s%n", Arrays.asList(Eon.values()));
// production code should handle this exception more gracefully
} catch (ClassNotFoundException x) {
x.printStackTrace();
}
}
}
</source>
Class: getFields()
<source lang="java">
/*
* Output:
Constructors:
public java.awt.Dimension(java.awt.Dimension) public java.awt.Dimension(int,int) public java.awt.Dimension()
Fields:
public int java.awt.Dimension.width public int java.awt.Dimension.height
Methods:
public int java.awt.Dimension.hashCode() public boolean java.awt.Dimension.equals(java.lang.Object) public java.lang.String java.awt.Dimension.toString() public java.awt.Dimension java.awt.Dimension.getSize() public void java.awt.Dimension.setSize(int,int) public void java.awt.Dimension.setSize(double,double) public void java.awt.Dimension.setSize(java.awt.Dimension) public double java.awt.Dimension.getHeight() public double java.awt.Dimension.getWidth() public java.lang.Object java.awt.geom.Dimension2D.clone() public void java.awt.geom.Dimension2D.setSize(java.awt.geom.Dimension2D) public final native java.lang.Class java.lang.Object.getClass() public final void java.lang.Object.wait() throws java.lang.InterruptedException public final void java.lang.Object.wait(long,int) throws java.lang.InterruptedException public final native void java.lang.Object.wait(long) throws java.lang.InterruptedException public final native void java.lang.Object.notify() public final native void java.lang.Object.notifyAll() * */
import java.lang.reflect.Constructor; import java.lang.reflect.Field; import java.lang.reflect.Method; public class MainClass {
public static void main(String args[]) {
try {
Class c = Class.forName("java.awt.Dimension");
System.out.println("Constructors:");
Constructor constructors[] = c.getConstructors();
for (int i = 0; i < constructors.length; i++) {
System.out.println(" " + constructors[i]);
}
System.out.println("Fields:");
Field fields[] = c.getFields();
for (int i = 0; i < fields.length; i++) {
System.out.println(" " + fields[i]);
}
System.out.println("Methods:");
Method methods[] = c.getMethods();
for (int i = 0; i < methods.length; i++) {
System.out.println(" " + methods[i]);
}
} catch (Exception e) {
System.out.println("Exception: " + e);
}
}
}
</source>
Class: getGenericInterfaces()
<source lang="java">
/*
* Copyright (c) 1995 - 2008 Sun Microsystems, Inc. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * - Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * - Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * - Neither the name of Sun Microsystems nor the names of its * contributors may be used to endorse or promote products derived * from this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */
import static java.lang.System.out; import java.lang.annotation.Annotation; import java.lang.reflect.Modifier; import java.lang.reflect.Type; import java.lang.reflect.TypeVariable; import java.util.ArrayList; import java.util.List; public class Main {
public static void main(String... args) {
try {
Class<?> c = Class.forName(args[0]);
out.format("Class:%n %s%n%n", c.getCanonicalName());
out.format("Modifiers:%n %s%n%n", Modifier.toString(c.getModifiers()));
out.format("Type Parameters:%n");
TypeVariable[] tv = c.getTypeParameters();
if (tv.length != 0) {
out.format(" ");
for (TypeVariable t : tv)
out.format("%s ", t.getName());
out.format("%n%n");
} else {
out.format(" -- No Type Parameters --%n%n");
}
out.format("Implemented Interfaces:%n");
Type[] intfs = c.getGenericInterfaces();
if (intfs.length != 0) {
for (Type intf : intfs)
out.format(" %s%n", intf.toString());
out.format("%n");
} else {
out.format(" -- No Implemented Interfaces --%n%n");
}
out.format("Inheritance Path:%n");
List<Class> l = new ArrayList<Class>();
printAncestor(c, l);
if (l.size() != 0) {
for (Class<?> cl : l)
out.format(" %s%n", cl.getCanonicalName());
out.format("%n");
} else {
out.format(" -- No Super Classes --%n%n");
}
out.format("Annotations:%n");
Annotation[] ann = c.getAnnotations();
if (ann.length != 0) {
for (Annotation a : ann)
out.format(" %s%n", a.toString());
out.format("%n");
} else {
out.format(" -- No Annotations --%n%n");
}
// production code should handle this exception more gracefully
} catch (ClassNotFoundException x) {
x.printStackTrace();
}
}
private static void printAncestor(Class<?> c, List<Class> l) {
Class<?> ancestor = c.getSuperclass();
if (ancestor != null) {
l.add(ancestor);
printAncestor(ancestor, l);
}
}
}
</source>
Class: getGenericSuperclass()
<source lang="java">
import java.lang.reflect.ParameterizedType; import java.lang.reflect.Type; import java.util.ArrayList; public class MainClass {
public static void main(String args[]) throws Exception {
Type type = StringList.class.getGenericSuperclass();
System.out.println(type); // java.util.ArrayList<java.lang.String>
ParameterizedType pt = (ParameterizedType) type;
System.out.println(pt.getActualTypeArguments()[0]);
}
} class StringList extends ArrayList<String> { }
</source>
Class: getInterfaces()
<source lang="java">
import java.util.Arrays; import javax.swing.JTable; public class Main {
public static void main(final String[] args) {
printMemberClasses(JTable.class);
}
public static void printMemberClasses(final Class dataType) {
final Class[] nestedClasses = dataType.getClasses();
final Class[] declaredNestedClasses = dataType.getDeclaredClasses();
final Class[] nestedInterfaces = dataType.getInterfaces();
final Class declaringClass = dataType.getDeclaringClass();
System.out.println("Member Class infor for: " + dataType.getName());
System.out.println("Nested Classes: " + Arrays.asList(nestedClasses));
System.out.println("Declared Nested Classes: " + Arrays.asList(declaredNestedClasses));
System.out.println("Interfaces: " + Arrays.asList(nestedInterfaces));
System.out.println("Declaring Class: " + declaringClass);
}
}
</source>
Class: getMethods()
<source lang="java">
/*
* Output:
Constructors:
public java.awt.Dimension(java.awt.Dimension) public java.awt.Dimension(int,int) public java.awt.Dimension()
Fields:
public int java.awt.Dimension.width public int java.awt.Dimension.height
Methods:
public int java.awt.Dimension.hashCode() public boolean java.awt.Dimension.equals(java.lang.Object) public java.lang.String java.awt.Dimension.toString() public java.awt.Dimension java.awt.Dimension.getSize() public void java.awt.Dimension.setSize(int,int) public void java.awt.Dimension.setSize(double,double) public void java.awt.Dimension.setSize(java.awt.Dimension) public double java.awt.Dimension.getHeight() public double java.awt.Dimension.getWidth() public java.lang.Object java.awt.geom.Dimension2D.clone() public void java.awt.geom.Dimension2D.setSize(java.awt.geom.Dimension2D) public final native java.lang.Class java.lang.Object.getClass() public final void java.lang.Object.wait() throws java.lang.InterruptedException public final void java.lang.Object.wait(long,int) throws java.lang.InterruptedException public final native void java.lang.Object.wait(long) throws java.lang.InterruptedException public final native void java.lang.Object.notify() public final native void java.lang.Object.notifyAll() * */
import java.lang.reflect.Constructor; import java.lang.reflect.Field; import java.lang.reflect.Method; public class MainClass {
public static void main(String args[]) {
try {
Class c = Class.forName("java.awt.Dimension");
System.out.println("Constructors:");
Constructor constructors[] = c.getConstructors();
for (int i = 0; i < constructors.length; i++) {
System.out.println(" " + constructors[i]);
}
System.out.println("Fields:");
Field fields[] = c.getFields();
for (int i = 0; i < fields.length; i++) {
System.out.println(" " + fields[i]);
}
System.out.println("Methods:");
Method methods[] = c.getMethods();
for (int i = 0; i < methods.length; i++) {
System.out.println(" " + methods[i]);
}
} catch (Exception e) {
System.out.println("Exception: " + e);
}
}
}
</source>
Class: getModifiers()
<source lang="java">
import java.lang.reflect.Modifier; public class Main {
public static void main(String[] args) throws Exception {
getClassModifier(String.class);
getClassModifier(TestA.class);
getClassModifier(TestB.class);
}
private static void getClassModifier(Class clazz) {
int modifier = clazz.getModifiers();
if (Modifier.isPrivate(modifier)) {
System.out.println(clazz.getName() + " class modifier is private");
}
}
protected static final class TestA {
}
private abstract class TestB {
}
}
</source>
Class: getName()
<source lang="java">
/*
* Output:
x is object of type: Class1 y is object of type: Class2 y"s superclass is Class1
* */
class Class1 {
int a; float b;
} class Class2 extends Class1 {
double c;
} public class MainClass {
public static void main(String args[]) {
Class1 x = new Class1();
Class2 y = new Class2();
Class clObj;
clObj = x.getClass(); // get Class reference
System.out.println("x is object of type: " + clObj.getName());
clObj = y.getClass(); // get Class reference
System.out.println("y is object of type: " + clObj.getName());
clObj = clObj.getSuperclass();
System.out.println("y"s superclass is " + clObj.getName());
}
}
</source>
Class: getPackage()
<source lang="java">
public class Main {
public static void main(String[] args) {
System.out.println(Main.class.getName());
System.out.println(int[].class.getName());
System.out.println(Main[].class.getName());
System.out.println(Main.class.getPackage());
}
}
</source>
Class: getProtectionDomain()
<source lang="java">
public class Main {
public static void main(String args[]) {
Main m = new Main();
System.out.println(m.getClass().getName() + " is loaded from "
+ m.getClass().getProtectionDomain().getCodeSource().getLocation());
}
}
</source>
Class: getResourceAsStream(String name)
<source lang="java">
import java.awt.Image; import java.awt.Toolkit; import java.io.BufferedInputStream; import java.io.ByteArrayOutputStream; import java.io.IOException; import java.io.InputStream; public final class MainClass {
private MainClass() {
}
public static Image getImage(Class relativeClass, String filename) {
Image returnValue = null;
InputStream is = relativeClass.getResourceAsStream(filename);
if (is != null) {
BufferedInputStream bis = new BufferedInputStream(is);
ByteArrayOutputStream baos = new ByteArrayOutputStream();
try {
int ch;
while ((ch = bis.read()) != -1) {
baos.write(ch);
}
returnValue = Toolkit.getDefaultToolkit().createImage(
baos.toByteArray());
} catch (IOException exception) {
System.err.println("Error loading: " + filename);
}
}
return returnValue;
}
}
</source>
Class: getResource(String name) (absolute from the classpath)
<source lang="java">
import java.net.URL; public class MainClass {
public static void main(String[] args) throws Exception {
// absolute from the classpath
URL url = MainClass.class.getResource("/mypackage/foo.txt");
System.out.println(url);
// relative to the class location
url = MainClass.class.getResource("foo.txt");
System.out.println(url);
// another relative document
url = MainClass.class.getResource("docs/bar.txt");
System.out.println(url);
}
}
</source>
Class: getResource(String name) (relative to the class location)
<source lang="java">
import java.net.URL; public class MainClass {
public static void main(String[] args) throws Exception {
// absolute from the classpath
URL url = MainClass.class.getResource("/mypackage/foo.txt");
System.out.println(url);
// relative to the class location
url = MainClass.class.getResource("foo.txt");
System.out.println(url);
// another relative document
url = MainClass.class.getResource("docs/bar.txt");
System.out.println(url);
}
}
</source>
Class: getSuperclass()
<source lang="java">
/*
* Output:
x is object of type: Class1 y is object of type: Class2 y"s superclass is Class1
* */
class Class1 {
int a; float b;
} class Class2 extends Class1 {
double c;
} public class MainClass {
public static void main(String args[]) {
Class1 x = new Class1();
Class2 y = new Class2();
Class clObj;
clObj = x.getClass(); // get Class reference
System.out.println("x is object of type: " + clObj.getName());
clObj = y.getClass(); // get Class reference
System.out.println("y is object of type: " + clObj.getName());
clObj = clObj.getSuperclass();
System.out.println("y"s superclass is " + clObj.getName());
}
}
</source>
Class: getTypeParameters()
<source lang="java">
import java.lang.reflect.TypeVariable; import java.util.List; public class MainClass {
public static void main(String args[]) throws Exception {
TypeVariable[] tv = List.class.getTypeParameters();
System.out.println(tv[0].getName());
}
}
</source>
Class: isArray()
<source lang="java">
/*
Output:
Array of: int Array size: 3
* */
import java.lang.reflect.Array; public class MainClass {
public static void main (String args[]) {
Object array = Array.newInstance(int.class, 3);
Class type = array.getClass();
if (type.isArray()) {
Class elementType = type.getComponentType();
System.out.println("Array of: " + elementType);
System.out.println("Array size: " + Array.getLength(array));
}
}
}
</source>
Class: isAssignableFrom(Class<?> cls)
<source lang="java">
import java.util.HashSet; import java.util.Iterator; import java.util.Set; public class Main {
public static boolean isNumber(final Class dataType) {
return Number.class.isAssignableFrom(dataType);
}
public static void main(final String[] args) {
final Set classes = new HashSet();
classes.add(Class.class);
System.out.println("Using isAssignableFrom:");
useAssignable(classes);
System.out.println("\nUsing isInstance:");
useIsInstance(classes);
}
public static void useAssignable(final Set inputSet) {
final Iterator iter = inputSet.iterator();
Object obj = null;
while (iter.hasNext()) {
obj = iter.next();
if (obj != null) {
if (Number.class.isAssignableFrom(obj.getClass())) {
System.out.println(obj);
}
}
}
}
public static void useIsInstance(final Set inputSet) {
final Iterator iter = inputSet.iterator();
Object obj = null;
while (iter.hasNext()) {
obj = iter.next();
if (Number.class.isInstance(obj)) {
System.out.println(obj);
}
}
}
public static void useIsInstance2(final Class dataType, final Set inputSet) {
if (dataType == null) {
throw new NullPointerException();
}
final Iterator iter = inputSet.iterator();
Object obj = null;
while (iter.hasNext()) {
obj = iter.next();
if (dataType.isInstance(obj)) {
System.out.println(obj);
}
}
}
}
</source>
Class: isEnum()
<source lang="java">
import org.xml.sax.XMLReader;
public class Main {
public static void main(String[] args) {
System.out.println(Size.class.isEnum());
System.out.println(String.class.isEnum());
System.out.println(String.class.isInstance("Test"));
System.out.println(XMLReader.class.isInterface());
}
} enum Size {
S, M, L, XL, XXL, XXXL;
}
</source>
Class: isInstance(Object obj)
<source lang="java">
import org.xml.sax.XMLReader;
public class Main {
public static void main(String[] args) {
System.out.println(Size.class.isEnum());
System.out.println(String.class.isEnum());
System.out.println(String.class.isInstance("Test"));
System.out.println(XMLReader.class.isInterface());
}
} enum Size {
S, M, L, XL, XXL, XXXL;
}
</source>
Class: isInterface()
<source lang="java">
/* java.util.List is an interface
*/
public class MainClass {
public static void main(String[] unused) {
try {
String n = "java.util.List";
Class c = Class.forName(n);
if (c.isInterface()) {
System.out.println(n + " is an interface");
} else {
System.out.println(n + " is not an interface");
}
} catch (Exception ex) {
ex.printStackTrace();
}
}
}
</source>
Class: Method getMethod(String name, Class<?>... parameterTypes)
<source lang="java">
import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; import java.lang.reflect.Method; @Retention(RetentionPolicy.RUNTIME) @interface MyAnnotation {
String stringValue(); int intValue();
} public class Main {
@MyAnnotation(stringValue = "Annotation Example", intValue = 100)
public static void myMethod() {
}
public static void main(String[] a) throws Exception {
Main ob = new Main();
Class c = ob.getClass();
Method m = c.getMethod("myMethod");
MyAnnotation anno = m.getAnnotation(MyAnnotation.class);
System.out.println(anno.stringValue() + " " + anno.intValue());
}
}
</source>
Class: newInstance()
<source lang="java">
public class Main {
public static void main(String[] args) {
try {
String pc = String.class.newInstance();
} catch (InstantiationException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
}
}
</source>
