class OuterClass {
private String aVariable = "Normal private variable.";
private static String staticVar = "private static variable.";
// Normal Inner class example.
class InnerClass {
public void aMethod() {
System.out.println("aMethod of InnerClass called.");
// Any Variable of the outer class is accessable from inner class.
System.out.println(" Accessing aVariable: " + aVariable);
System.out.println();
}
}
// Static Inner class example.
static class staticInnerClass {
void aMethod() {
System.out.println("aMethod of staticInnerClass called.");
// Only Static Variable of the outer class is accessable from inner
// class.
System.out.println(" Accessing a static Variable:" + staticVar);
System.out.println();
}
}
// Method-Local Inner Class example.
public void aMethod() {
final String msg = "Method-Local Inner Classes";
System.out.println("aMethod from the OuterClass called.");
// Method-Local Inner Class
class MethodLocalInnerClass {
String variable = "MethodLocalInnerClass variable.";
void aMethod() {
System.out
.println("aMethod from the MethodLocalInnerClass called.");
// Can access final local variable declared in the method.
System.out
.println(" Accessing a local Variable in the method: "
+ msg);
System.out.println();
}
}
// initialization of Method-Local Inner Class
MethodLocalInnerClass methodLocalInnerClass = new MethodLocalInnerClass();
System.out.println("variable from the MethodLocalInnerClass: "
+ methodLocalInnerClass.variable);
methodLocalInnerClass.aMethod();
}
public void initInnerClass() {
// Normal invocation of InnerClass works within the outer class
InnerClass innerClass = new InnerClass();
innerClass.aMethod();
}
}
class DemoClass {
public void aMethod() {
System.out.println("aMethod called from demoClass");
}
}
interface DemoInterface {
void aMethod();
}
class MethodArgInnerClass {
public void anotherMethod(DemoInterface demoInterface) {
System.out.println("anotherMethod of methodArgInnerClass called.");
demoInterface.aMethod();
}
}
public class InnerClassSample {
public static void main(String[] args) {
// Get a reference to outer class.
OuterClass outerClass = new OuterClass();
// initialization of Normal Inner class
OuterClass.InnerClass innerClass = outerClass.new InnerClass();
innerClass.aMethod();
// initialization of Static Inner class
OuterClass.staticInnerClass innerClass2 = new OuterClass.staticInnerClass();
innerClass2.aMethod();
// Demo of Method-Local Inner Class
outerClass.aMethod();
// Following are the demo of Anonymous Inner class in action.
/**
* Example of overriding the method: This anonymous class now
* becomes the subclass of the DemoClass.java
*/
DemoClass demoClass = new DemoClass() {
public void aMethod() {
System.out.println("aMethod over ridden from "
+ "Anonymous Inner class of demoClass");
}
};
demoClass.aMethod();
// Example of implementing a Interface
DemoInterface interface1 = new DemoInterface() {
public void aMethod() {
System.out.println("aMethod method of the DemoInterface "
+ "implemented by Anonymous Inner class");
}
};
interface1.aMethod();
// Example of Anonymous Inner class in method argument.
MethodArgInnerClass innerClass3 = new MethodArgInnerClass();
innerClass3.anotherMethod(new DemoInterface() {
public void aMethod() {
System.out.println("Example of Anonymous Inner class"
+ " in method argument");
}
});
}
}
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