Java Generics - Map

Java has provided generic support in Map interface.

Syntax

Set<T> set = new HashSet<T>();

Where

• set − object of Set Interface.

• T − The generic type parameter passed during set declaration.

Description

The T is a type parameter passed to the generic interface Set and its implemenation class HashSet.

Example

Create the following java program using any editor of your choice.

package com.howcodex;

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

public class GenericsTester {
   public static void main(String[] args) {

      Map<Integer,Integer> integerMap 
         = new HashMap<Integer,Integer>();
  
      integerMap.put(1, 10);
      integerMap.put(2, 11);

      Map<String,String> stringMap = new HashMap<String,String>();
    
      stringMap.put("1", "Hello World");
      stringMap.put("2","Hi World");
 

      System.out.printf("Integer Value :%d\n", integerMap.get(1));
      System.out.printf("String Value :%s\n", stringMap.get("1"));

      // iterate keys.
      Iterator<Integer> integerIterator   = integerMap.keySet().iterator();

      while(integerIterator.hasNext()) {
         System.out.printf("Integer Value :%d\n", integerIterator.next());
      }

      // iterate values.
      Iterator<String> stringIterator   = stringMap.values().iterator();

      while(stringIterator.hasNext()) {
         System.out.printf("String Value :%s\n", stringIterator.next());
      }
   }  
}

This will produce the following result −

Output

Integer Value :10
String Value :Hello World
Integer Value :1
Integer Value :2
String Value :Hello World
String Value :Hi World