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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());
}
}
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| Output: |
Type: java.lang.String
Type: java.lang.Boolean
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Java Generics Sample Code Examples
- Write a simple generics class example.
- Write a simple generics class example with two type parameters.
- How implement bounded types (extend superclass) with generics?
- How implement bounded types (implements an interface) with generics?
- What is generics wildcard arguments? Give an example.
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What is abstract class or abstract method?
We cannot create instance for an abstract class. We can able to create
instance for its subclass only. By specifying abstract keyword just before
class, we can make a class as abstract class.
public abstract class MyAbstractClass{
}
Abstract class may or may not contains abstract methods. Abstract method is
just method signature, it does not containes any implementation. Its subclass
must provide implementation for abstract methods. Abstract methods are looks
like as given below:
public abstract int getLength();
The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails.
-- William Arthur Ward
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