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Program: How implement bounded types (implements an interface) with generics?
As of now we have seen examples for only one type parameter. What happens in case we want to access
group of objects comes from same family, means implementing same interface? You can restrict the generics type parameter to
a certain group of objects which implements same interface. You can achieve this my specifying extends <interface-name> at class
definitions, look at the example, it gives you more comments to understand. You can also specify multiple interfaces at the definision.
you can do this by specifying mulitple interfaces seperated by "&". You can also specify class which implements an interface and the interface
together. For example:
class MyClass<T extends TestClass & TestInterface> {
Look at example for more understanding.
package com.java2novice.generics;
public class MyBoundedInterface {
public static void main(String a[]){
//Creating object of implementation class X called Y and
//passing it to BoundExmp as a type parameter.
BoundExmp<Y> bey = new BoundExmp<Y>(new Y());
bey.doRunTest();
//Creating object of implementation class X called Z and
//passing it to BoundExmp as a type parameter.
BoundExmp<Z> bez = new BoundExmp<Z>(new Z());
bez.doRunTest();
//If you uncomment below code it will throw compiler error
//becasue we restricted to only of type X implementation classes.
//BoundExmp<String> bes = new BoundExmp<String>(new String());
//bea.doRunTest();
}
}
class BoundExmp<T extends X>{
private T objRef;
public BoundExmp(T obj){
this.objRef = obj;
}
public void doRunTest(){
this.objRef.printClass();
}
}
interface X{
public void printClass();
}
class Y implements X{
public void printClass(){
System.out.println("I am in class Y");
}
}
class Z implements X{
public void printClass(){
System.out.println("I am in class Z");
}
}
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Output: |
I am in class Y
I am in class Z
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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 race condition?
A race condition is a situation in which two or more threads or
processes are reading or writing some shared data, and the final
result depends on the timing of how the threads are scheduled.
Race conditions can lead to unpredictable results and subtle
program bugs. A thread can prevent this from happening by locking
an object. When an object is locked by one thread and another
thread tries to call a synchronized method on the same object,
the second thread will block until the object is unlocked.
Be yourself; everyone else is already taken.
-- Oscar Wilde
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