class model generics code example

Example 1: generics Interface in java

/*In similar way, we can create generic interfaces in java. We can also have multiple type parameters as in Map interface. Again we can provide parameterized value to a parameterized type also, for example new HashMap<String, List<String>>(); is valid.*/
package java.lang;
import java.util.*;

public interface Comparable<T> {
    public int compareTo(T o);
}

Example 2: generics Interface in java

/*Sometimes we don’t want the whole class to be parameterized, in that case, we can create java generics method. Since the constructor is a special kind of method, we can use generics type in constructors too.

Here is a class showing an example of a java generic method.

Notice the isEqual method signature showing syntax to use generics type in methods. Also, notice how to use these methods in our java program. We can specify type while calling these methods or we can invoke them like a normal method. Java compiler is smart enough to determine the type of variable to be used, this facility is called type inference.*/


package com.journaldev.generics;

public class GenericsMethods {

	//Java Generic Method
	public static <T> boolean isEqual(GenericsType<T> g1, GenericsType<T> g2){
		return g1.get().equals(g2.get());
	}
	
	public static void main(String args[]){
		GenericsType<String> g1 = new GenericsType<>();
		g1.set("Pankaj");
		
		GenericsType<String> g2 = new GenericsType<>();
		g2.set("Pankaj");
		
		boolean isEqual = GenericsMethods.<String>isEqual(g1, g2);
		//above statement can be written simply as
		isEqual = GenericsMethods.isEqual(g1, g2);
		//This feature, known as type inference, allows you to invoke a generic method as an ordinary method, without specifying a type between angle brackets.
		//Compiler will infer the type that is needed
	}
}