JAVA EXAMPLE PROGRAMS

JAVA EXAMPLE PROGRAMS

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Program: Write a simple generics class example.


Below example shows how to create a simple generics class. We have created SimpleGeneric class, which accepts single type parameter. Look at the generics class definition, the type parameter should be followed by class name and should contain with in <>, here T defines the type parameter. You can find comments at example itself.


package com.java2novice.generics;

public class MySimpleGenerics {

	public static void main(String a[]){
		
		//we are going to create SimpleGeneric object with String as type parameter
		SimpleGeneric<String> sgs = new SimpleGeneric<String>("JAVA2NOVICE");
		sgs.printType();
		//we are going to create SimpleGeneric object with Boolean as type parameter
		SimpleGeneric<Boolean> sgb = new SimpleGeneric<Boolean>(Boolean.TRUE);
		sgb.printType();
	}
}

/**
 * Here T is a type parameter, and it will be replaced with 
 * actual type when the object got created. 
 */
class SimpleGeneric<T>{
	
	//declaration of object type T
	private T objReff = null;
	
	//constructor to accept type parameter T
	public SimpleGeneric(T param){
		this.objReff = param;
	}
	
	public T getObjReff(){
		return this.objReff;
	}
	
	//this method prints the holding parameter type
	public void printType(){
		System.out.println("Type: "+objReff.getClass().getName());
	}
}

Output:
Type: java.lang.String
Type: java.lang.Boolean
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Java Generics Sample Code Examples

  1. Write a simple generics class example.
  2. Write a simple generics class example with two type parameters.
  3. How implement bounded types (extend superclass) with generics?
  4. How implement bounded types (implements an interface) with generics?
  5. What is generics wildcard arguments? Give an example.
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As you know, destory() is part of servlet life cycle methods, it is used to kill the servlet instance. Servlet Engine is used to call destory(). In case, if you call destory method from service(), it just execute the code written in the destory(), but it wont kill the servlet instance. destroy() will be called before killing the servlet instance by servlet engine.
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Reference: Java™ Platform Standard Ed. 7 - API Specification | Java is registered trademark of Oracle.
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