Java Generic Interface Examples

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In this article, we will learn how to write a generic interface with examples.

The Generalized Syntax for a Generic Interface

interface interfaceName<type-param-list> { // ...
}

class className<type-param-list>
           implements interfaceName<type-param-list> {
     // ....
}

• type-param-list is a comma-separated list of type parameters.
• when a generic interface is implemented, you must specify the type arguments

Java Generic Interface Examples

Let's write a simple example to find the minimum and the maximum value of Integer, character and String array.

1. Create three arrays - Integer, character and String array.
2. Write generic methods to find the minimum and a maximum value of any type of array.

/**
 * Generic interface example to find min and max of array.
 * @author javaguides.net
 *
 */
public class GenericInterfaceExample {
    public static void main(String args[]) {
         Integer intOfArray[] = { 3, 6, 2, 8, 6 };
         Character charOfArray[] = { 'A', 'r', 'V', 'w' };
         String strOfArray[] = {"abc", "xyz", "pqr"};
  
         MinMaxImpl<Integer> intMinMax = new MinMaxImpl<Integer>(intOfArray);
         MinMaxImpl<Character> charMinMax = new MinMaxImpl<Character>(charOfArray);
         MinMaxImpl<String> strMinMax = new MinMaxImpl<String>(strOfArray);

         System.out.println("Max value in intOfArray: " + intMinMax.max());
         System.out.println("Min value in intOfArray: " + intMinMax.min());

         System.out.println("Max value in charOfArray: " + charMinMax.max());
         System.out.println("Min value in charOfArray: " + charMinMax.min());
  
         System.out.println("Max value in strOfArray: " + strMinMax.max());
         System.out.println("Min value in strOfArray: " + strMinMax.min());
     }
}

interface MinMax<T extends Comparable<T>> {
     T min();

     T max();
}

class MinMaxImpl<T extends Comparable<T>> implements MinMax<T> {
     T[] vals;

     MinMaxImpl(T[] o) {
         vals = o;
     }

     public T min() {
         T v = vals[0];

         for (int i = 1; i < vals.length; i++) {
             if (vals[i].compareTo(v) < 0) {
                  v = vals[i];
             }
         }

          return v;
     }

     public T max() {
          T v = vals[0];

          for (int i = 1; i < vals.length; i++) {
             if (vals[i].compareTo(v) > 0) {
                  v = vals[i];
             }
          }

          return v;
     }
}

Output:

Max value in intOfArray: 8
Min value in intOfArray: 2
Max value in charOfArray: w
Min value in charOfArray: A
Max value in strOfArray: xyz
Min value in strOfArray: abc

Related Java Generics Examples

Java Generics Upper Bounded Wildcards Example
Java Generics Lower Bounded Wildcards Example
Java Generic Methods Examples
Java Generic Interface Examples
Java Generic Class Examples
Java Generics Multiple Type Parameters Example

Java Generics Wildcards Example

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