Admin: 1 версия

2010-06-01T05:19:17Z

1 версия

в 17:44, 31 мая 2010

2010-05-31T17:44:27Z

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== implements Externalizable ==



<source lang="java">
import java.io.Externalizable;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectInputStream;
import java.io.ObjectOutput;
import java.io.ObjectOutputStream;
public class MainClass {
public static void main(String[] args) throws IOException, ClassNotFoundException {
System.out.println("Constructing objects:");
MyBean myBean = new MyBean("A String ", 47);
System.out.println(myBean);
ObjectOutputStream o = new ObjectOutputStream(new FileOutputStream("MyBean.out"));
System.out.println("Saving object:");
o.writeObject(myBean);
o.close();

ObjectInputStream in = new ObjectInputStream(new FileInputStream("MyBean.out"));
System.out.println("Recovering:");
myBean = (MyBean) in.readObject();
System.out.println(myBean);
}
}
class MyBean implements Externalizable {
private int i;
private String s; // No initialization
public MyBean() {
System.out.println("MyBean Constructor");
// s, i not initialized
}
public MyBean(String x, int a) {
System.out.println("MyBean(String x, int a)");
s = x;
i = a;
// s & i initialized only in nondefault constructor.
}
public String toString() {
return s + i;
}
public void writeExternal(ObjectOutput out) throws IOException {
System.out.println("MyBean.writeExternal");
out.writeObject(s);
out.writeInt(i);
}
public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {
System.out.println("MyBean.readExternal");
s = (String) in.readObject();
i = in.readInt();
}
}
/**/</source>



<pre class=codeResult>Constructing objects:
MyBean(String x, int a)
A String 47
Saving object:
MyBean.writeExternal
Recovering:
MyBean Constructor
MyBean.readExternal
A String 47</pre>

== Reconstructing an externalizable object ==



<source lang="java">
import java.io.Externalizable;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectInputStream;
import java.io.ObjectOutput;
import java.io.ObjectOutputStream;
public class MainClass {
public static void main(String[] args) throws IOException, ClassNotFoundException {
System.out.println("Constructing objects:");
MyBean myBean = new MyBean("A String ", 47);
System.out.println(myBean);
ObjectOutputStream o = new ObjectOutputStream(new FileOutputStream("MyBean.out"));
System.out.println("Saving object:");
o.writeObject(myBean);
o.close();

ObjectInputStream in = new ObjectInputStream(new FileInputStream("MyBean.out"));
System.out.println("Recovering:");
myBean = (MyBean) in.readObject();
System.out.println(myBean);
}
}
class MyBean implements Externalizable {
private int i;
private String s; // No initialization
public MyBean() {
System.out.println("MyBean Constructor");
// s, i not initialized
}
public MyBean(String x, int a) {
System.out.println("MyBean(String x, int a)");
s = x;
i = a;
// s & i initialized only in nondefault constructor.
}
public String toString() {
return s + i;
}
public void writeExternal(ObjectOutput out) throws IOException {
System.out.println("MyBean.writeExternal");
out.writeObject(s);
out.writeInt(i);
}
public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {
System.out.println("MyBean.readExternal");
s = (String) in.readObject();
i = in.readInt();
}
}
/**/</source>



<pre class=codeResult>Constructing objects:
MyBean(String x, int a)
A String 47
Saving object:
MyBean.writeExternal
Recovering:
MyBean Constructor
MyBean.readExternal
A String 47</pre>

== Simple use of Externalizable ==



<source lang="java">
import java.io.Externalizable;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectInputStream;
import java.io.ObjectOutput;
import java.io.ObjectOutputStream;
class A implements Externalizable {
public A() {
System.out.println("A Constructor");
}
public void writeExternal(ObjectOutput out) throws IOException {
System.out.println("A.writeExternal");
}
public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {
System.out.println("A.readExternal");
}
}
class B implements Externalizable {
B() {
System.out.println("B Constructor");
}
public void writeExternal(ObjectOutput out) throws IOException {
System.out.println("B.writeExternal");
}
public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {
System.out.println("B.readExternal");
}
}
public class MainClass {
public static void main(String[] args) throws IOException, ClassNotFoundException {
System.out.println("Constructing objects:");
A b1 = new A();
B b2 = new B();
ObjectOutputStream o = new ObjectOutputStream(new FileOutputStream("File.out"));
System.out.println("Saving objects:");
o.writeObject(b1);
o.writeObject(b2);
o.close();
ObjectInputStream in = new ObjectInputStream(new FileInputStream("File.out"));
System.out.println("Recovering b1:");
b1 = (A) in.readObject();
}
}
/*
*/</source>



<pre class=codeResult>Constructing objects:
A Constructor
B Constructor
Saving objects:
A.writeExternal
B.writeExternal
Recovering b1:
A Constructor
A.readExternal</pre>

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Admin: 1 версия

в 17:44, 31 мая 2010