Create a generic interface, a generic abstract class and a generic class. Each of them will take 2 generic parameters. First parameter must be a class and the 2nd parameter must be an interface code example

Example 1: generics Interface in java

/*Notice that while using this class, we have to use type casting and it can produce ClassCastException at runtime. Now we will use java generic class to rewrite the same class as shown below.*/
package com.journaldev.generics;

public class GenericsType<T> {

	private T t;
	
	public T get(){
		return this.t;
	}
	
	public void set(T t1){
		this.t=t1;
	}
	
	public static void main(String args[]){
		GenericsType<String> type = new GenericsType<>();
		type.set("Pankaj"); //valid
		
		GenericsType type1 = new GenericsType(); //raw type
		type1.set("Pankaj"); //valid
		type1.set(10); //valid and autoboxing support
	}
}
/*Notice the use of GenericsType class in the main method. We don’t need to do type-casting and we can remove ClassCastException at runtime. If we don’t provide the type at the time of creation, the compiler will produce a warning that “GenericsType is a raw type.

References to generic type GenericsType<T> should be parameterized”. When we don’t provide the type, the type becomes Object and hence it’s allowing both String and Integer objects. But, we should always try to avoid this because we will have to use type casting while working on raw type that can produce runtime errors.

Tip: We can use @SuppressWarnings("rawtypes") annotation to suppress the compiler warning, check out java annotations tutorial.*/

Example 2: generics Interface in java

/*We can define our own classes with generics type. A generic type is a class or interface that is parameterized over types. We use angle brackets (<>) to specify the type parameter.

To understand the benefit, let’s say we have a simple class as:*/
package com.journaldev.generics;

public class GenericsTypeOld {

	private Object t;

	public Object get() {
		return t;
	}

	public void set(Object t) {
		this.t = t;
	}

        public static void main(String args[]){
		GenericsTypeOld type = new GenericsTypeOld();
		type.set("Pankaj"); 
		String str = (String) type.get(); //type casting, error prone and can cause ClassCastException
	}
}