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
 Next Program >>

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.
Knowledge Centre
Different types of Access Modifiers
public: Any thing declared as public can be accessed from anywhere.

private: Any thing declared as private can't be seen outside of its class.

protected: Any thing declared as protected can be accessed by classes in the same package and subclasses in the other packages.

default modifier: Can be accessed only to classes in the same package.
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About Author

I'm Nataraja Gootooru, programmer by profession and passionate about technologies. All examples given here are as simple as possible to help beginners. The source code is compiled and tested in my dev environment.

If you come across any mistakes or bugs, please email me to [email protected].

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Reference: Java™ Platform Standard Ed. 7 - API Specification | Java™ Platform Standard Ed. 8 - API Specification | Java is registered trademark of Oracle.
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