Java WeakHashMap get() Method

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Description

The Java WeakHashMap get(Object key) method is used to return the value to which the specified key is mapped in this weak hash map, or null if the map contains no mapping for this key.

Declaration

Following is the declaration for java.util.WeakHashMap.get() method.

public Object get(Object key)

Parameters

key − the key whose associated value is to be returned.

Return Value

The method call returns the value to which this map maps the specified key, or null if the map contains no mapping for this key.

Exception

NA

Getting a Value based on a Key in a WeakHashMap of Integer, Integer Pairs Example

The following example shows the usage of Java WeakHashMap get() method to get a value based on a key from a Map. We've created a Map object of Integer,Integer pairs. Then few entries are added, map is printed. Using get() method, a value is retrieved and printed.

package com.tutorialspoint;

import java.util.WeakHashMap;

public class WeakHashMapDemo {
   public static void main(String args[]) {
      
      // create hash map
      WeakHashMap<Integer,Integer> newmap = new WeakHashMap<>();

      // populate hash map
      newmap.put(1, 1);
      newmap.put(2, 2);
      newmap.put(3, 3); 

      System.out.println("Initial map elements: " + newmap);

      System.out.println("Value: " + newmap.get(1));
   }
}

Output

Let us compile and run the above program, this will produce the following result.

Initial map elements: {3=3, 2=2, 1=1}
Value: 1

Getting a Value based on a Key in a WeakHashMap of Integer, String Pairs Example

The following example shows the usage of Java WeakHashMap get() method to get a value based on a key from a Map. We've created a Map object of Integer,String pairs. Then few entries are added, map is printed. Using get() method, a value is retrieved and printed.

package com.tutorialspoint;

import java.util.WeakHashMap;

public class WeakHashMapDemo {
   public static void main(String args[]) {
      
      // create hash map
      WeakHashMap<Integer,String> newmap = new WeakHashMap<>();

      // populate hash map
      newmap.put(1, "tutorials");
      newmap.put(2, "point");
      newmap.put(3, "is best"); 

      System.out.println("Initial map elements: " + newmap);

      System.out.println("Value: " + newmap.get(1));
   }
}

Output

Let us compile and run the above program, this will produce the following result.

Initial map elements: {3=is best, 2=point, 1=tutorials}
Value: tutorials

Getting a Value based on a Key in a WeakHashMap of Integer, Object Pairs Example

The following example shows the usage of Java WeakHashMap get() method to get a value based on a key from a Map. We've created a Map object of Integer,Student pair. Then few entries are added, map is printed. Using get() method, a value is retrieved and printed.

package com.tutorialspoint;

import java.util.WeakHashMap;

public class WeakHashMapDemo {
   public static void main(String args[]) {
      
      // create hash map
      WeakHashMap<Integer,Student> newmap = new WeakHashMap<>();

      // populate hash map
      newmap.put(1, new Student(1, "Julie"));
      newmap.put(2, new Student(2, "Robert"));
      newmap.put(3, new Student(3, "Adam"));

      System.out.println("Initial map elements: " + newmap);

      System.out.println("Value: " + newmap.get(1));
   }
}
class Student {
   int rollNo;
   String name;

   Student(int rollNo, String name){
      this.rollNo = rollNo;
      this.name = name;
   }

   @Override
   public String toString() {
      return "[ " + this.rollNo + ", " + this.name + " ]";
   }
}

Output

Let us compile and run the above program, this will produce the following result.

Initial map elements: {3=[ 3, Adam ], 2=[ 2, Robert ], 1=[ 1, Julie ]}
Value: [ 1, Julie ]