Java Tutorial/JSP/Class in JSP Page
Содержание
- 1 Calling Superclass Constructors
- 2 Calling Superclass Constructors
- 3 Creating a Java Interface
- 4 Overloading Methods
- 5 Overriding Methods
- 6 Runtime Polymorphism
- 7 Using Abstract Classes
- 8 Using Inheritance
- 9 Using Parameterized Constructors
- 10 Using Restricted Access
- 11 Using Superclass Variables With Subclassed Objects
- 12 Working With Constructors and Inheritance
Calling Superclass Constructors
<source lang="java">
<HTML>
<HEAD>
<TITLE>Calling Superclass Constructors</TITLE>
</HEAD>
<BODY>
Calling Superclass Constructors
<%!
javax.servlet.jsp.JspWriter localOut;
class a
{
a() throws java.io.IOException
{
localOut.println("In a\"s constructor...
");
}
}
class b extends a
{
b() throws java.io.IOException
{
localOut.println("In b\"s constructor...
");
}
}
%>
<%
localOut = out;
b obj = new b();
%>
</BODY>
</HTML></source>
Creating a Java Interface
<source lang="java">
<HTML>
<HEAD>
<TITLE>Creating a Java Interface</TITLE>
</HEAD>
<BODY>
Creating a Java Interface
<%!
javax.servlet.jsp.JspWriter localOut;
interface Printem
{
void printText() throws java.io.IOException;
}
class a implements Printem
{
public void printText() throws java.io.IOException
{
localOut.println("Hello from JSP!");
}
}
%>
<%
localOut = out;
a printer = new a();
printer.printText();
%>
</BODY>
</HTML></source>
Overloading Methods
<source lang="java">
<HTML>
<HEAD>
<TITLE>Overloading Methods</TITLE>
</HEAD>
<BODY>
Overloading Methods
<%!
javax.servlet.jsp.JspWriter localOut;
void printText() throws java.io.IOException
{
localOut.println("Hello!
");
}
void printText(String s) throws java.io.IOException
{
localOut.println(s + "
");
}
%>
<%
localOut = out;
printText();
printText("Hello from JSP!");
%>
</BODY>
</HTML></source>
Overriding Methods in derived class
<source lang="java">
<HTML>
<HEAD>
<TITLE>Overriding Methods in derived class</TITLE>
</HEAD>
<BODY>
Overriding Methods
<%!
javax.servlet.jsp.JspWriter localOut;
class BaseClass
{
public void print() throws java.io.IOException
{
localOut.println("print in base...
");
}
}
class DerivedClass extends BaseClass
{
public void print() throws java.io.IOException
{
localOut.println("print in Derived class...
");
}
}
%>
<%
localOut = out;
out.println("Creating an animal object...
");
BaseClass a = new BaseClass();
a.print();
out.println();
out.println("Creating a trout object...
");
DerivedClass t = new DerivedClass();
t.print();
%>
</BODY>
</HTML></source>
Runtime Polymorphism
<source lang="java">
<HTML>
<HEAD>
<TITLE>Runtime Polymorphism</TITLE>
</HEAD>
<BODY>
Runtime Polymorphism
<%!
javax.servlet.jsp.JspWriter localOut;
class BaseClass
{
public void print() throws java.io.IOException
{
localOut.println("Hello from BaseClass...
");
}
}
class DerivedClass1 extends BaseClass
{
public void print() throws java.io.IOException
{
localOut.println("Hello from DerivedClass1...
");
}
}
class DerivedClass2 extends BaseClass
{
public void print() throws java.io.IOException
{
localOut.println("Hello from DerivedClass2...
");
}
}
class DerivedClass3 extends BaseClass
{
public void print() throws java.io.IOException
{
localOut.println("Hello from DerivedClass3...
");
}
}
%>
<%
localOut = out;
BaseClass a1 = new BaseClass();
DerivedClass1 b1 = new DerivedClass1();
DerivedClass2 c1 = new DerivedClass2();
DerivedClass3 d1 = new DerivedClass3();
BaseClass baseClassVariable;
baseClassVariable = a1;
baseClassVariable.print();
baseClassVariable = b1;
baseClassVariable.print();
baseClassVariable = c1;
baseClassVariable.print();
baseClassVariable = d1;
baseClassVariable.print();
%>
</BODY>
</HTML></source>
Using Abstract Classes
<source lang="java">
<HTML>
<HEAD>
<TITLE>Using Abstract Classes</TITLE>
</HEAD>
<BODY>
Using Abstract Classes
<%!
javax.servlet.jsp.JspWriter localOut;
abstract class a
{
abstract String getText() throws java.io.IOException;
public void printem() throws java.io.IOException
{
localOut.println(getText());
}
}
class b extends a
{
String getText() throws java.io.IOException
{
return "Hello from JSP!";
}
}
%>
<%
localOut = out;
b bObject = new b();
bObject.printem();
%>
</BODY>
</HTML></source>
Using Inheritance
<source lang="java">
<HTML>
<HEAD>
<TITLE>Using Inheritance</TITLE>
</HEAD>
<BODY>
Using Inheritance
<%!
javax.servlet.jsp.JspWriter localOut;
class BaseClass
{
public void start() throws java.io.IOException
{
localOut.println("Starting...
");
}
}
class DerivedClass extends BaseClass
{
public void drive() throws java.io.IOException
{
localOut.println("Deriving...
");
}
}
%>
<%
localOut = out;
out.println("Creating an DerivedClass...
");
DerivedClass a = new DerivedClass();
a.start();
a.drive();
%>
</BODY>
</HTML></source>
Using Parameterized Constructors
<source lang="java">
<HTML>
<HEAD>
<TITLE>Using Parameterized Constructors</TITLE>
</HEAD>
<BODY>
Using Parameterized Constructors
<%!
javax.servlet.jsp.JspWriter localOut;
class a
{
a() throws java.io.IOException
{
localOut.println("In a\"s constructor...
");
}
}
class b extends a
{
b(String s) throws java.io.IOException
{
localOut.println("In b\"s String constructor...
");
localOut.println(s);
}
}
%>
<%
localOut = out;
b obj = new b("Hello from JSP!
");
%>
</BODY>
</HTML></source>
Using Restricted Access
<source lang="java">
<HTML>
<HEAD>
<TITLE>Using Restricted Access</TITLE>
</HEAD>
<BODY>
Using Restricted Access
<%!
javax.servlet.jsp.JspWriter localOut;
class BaseClass
{
protected void start() throws java.io.IOException
{
localOut.println("Starting...
");
}
}
class DerivedClass extends BaseClass
{
public void drive() throws java.io.IOException
{
localOut.println("Driving...
");
}
}
%>
<%
localOut = out;
out.println("Creating an DerivedClass...
");
DerivedClass a = new DerivedClass();
a.start();
a.drive();
%>
</BODY>
</HTML></source>
Using Superclass Variables With Subclassed Objects
<source lang="java">
<HTML>
<HEAD>
<TITLE>Using Superclass Variables With Subclassed Objects</TITLE>
</HEAD>
<BODY>
Using Superclass Variables With Subclassed Objects
<%!
javax.servlet.jsp.JspWriter localOut;
class BaseClass
{
public void start() throws java.io.IOException
{
localOut.println("Starting...
");
}
}
class DerivedClass1 extends BaseClass
{
public void fly() throws java.io.IOException
{
localOut.println("Flying...
");
}
}
class DerivedClass2 extends DerivedClass1
{
public void fly() throws java.io.IOException
{
localOut.println("Flying...
");
}
}
%>
<%
localOut = out;
out.println();
out.println("Creating a DerivedClass2 object...
");
BaseClass p = new DerivedClass2();
p.start();
%>
</BODY>
</HTML></source>
Working With Constructors and Inheritance
<source lang="java">
<HTML>
<HEAD>
<TITLE>Working With Constructors and Inheritance</TITLE>
</HEAD>
<BODY>
Working With Constructors and Inheritance
<%!
javax.servlet.jsp.JspWriter localOut;
class BaseClass
{
BaseClass() throws java.io.IOException
{
localOut.println("In a\"s constructor...
");
}
BaseClass(String s) throws java.io.IOException
{
localOut.println("In a\"s String constructor...
");
localOut.println(s);
}
}
class DerivedClass extends BaseClass
{
DerivedClass(String s) throws java.io.IOException
{
super(s);
localOut.println("In b\"s String constructor...
");
localOut.println(s);
}
}
%>
<%
localOut = out;
DerivedClass obj = new DerivedClass("Hello from JSP!
");
%>
</BODY>
</HTML></source>
