Java TreeMap get() Method

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Description

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

Declaration

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

public V get(Object key)

Parameters

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

Return Value

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

Exception

• ClassCastException − This exception is thrown if the specified key cannot be compared with the keys currently in the map.

• NullPointerException − This exception is thrown if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys.

Getting a Value for a given Key from a TreeMap of Integer, Integer Pairs Example

The following example shows the usage of Java TreeMap get() method to get the value associated with the given key in the map. We've created a TreeMap object of Integer,Integer pairs. Then few entries are added, and using get() we're printing a value for a given key.

package com.tutorialspoint;

import java.util.TreeMap;

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

      // creating tree map 
      TreeMap<Integer, Integer> treemap = new TreeMap<>();

      // populating tree map
      treemap.put(2, 2);
      treemap.put(1, 1);
      treemap.put(3, 3);
      treemap.put(6, 6);
      treemap.put(5, 5);

      System.out.println("Checking value for key 3");
      System.out.println("Value is: "+ treemap.get(3));
   }    
}

Output

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

Checking value for key 3
Value is: three

Getting a Value for a given Key from a TreeMap of Integer, String Pairs Example

The following example shows the usage of Java TreeMap get() method to get the value associated with the given key in the map. We've created a TreeMap object of Integer,String pairs. Then few entries are added, and using get() we're printing a value for a given key.

package com.tutorialspoint;

import java.util.TreeMap;

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

      // creating tree map 
      TreeMap<Integer, String> treemap = new TreeMap<>();

      // populating tree map
      treemap.put(2, "two");
      treemap.put(1, "one");
      treemap.put(3, "three");
      treemap.put(6, "six");
      treemap.put(5, "five");

      System.out.println("Checking value for key 3");
      System.out.println("Value is: "+ treemap.get(3));
   }    
}

Output

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

Checking value for key 3
Value is: three

Getting a Value for a given Key from a TreeMap of Integer, Object Pairs Example

The following example shows the usage of Java TreeMap get() method to get the value associated with the given key in the map. We've created a TreeMap object of Integer,Student pairs. Then few entries are added, and using get() we're printing a value for a given key.

package com.tutorialspoint;

import java.util.TreeMap;

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

      // creating tree map 
      TreeMap<Integer, Student> treemap = new TreeMap<>();

      // populating tree map
      treemap.put(2, new Student(2, "Robert"));
      treemap.put(1, new Student(1, "Julie"));  
      treemap.put(3, new Student(3, "Adam"));
      treemap.put(6, new Student(5, "Julia"));
      treemap.put(5, new Student(5, "Tom"));

      System.out.println("Checking value for key 3");
      System.out.println("Value is: "+ treemap.get(3));
   }    
}
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 + " ]";
   }
   @Override
   public boolean equals(Object obj) {
      if(obj == null) return false;
      Student s = (Student)obj;
      return this.rollNo == s.rollNo && this.name.equalsIgnoreCase(s.name);
   }
}

Output

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

Checking value for key 3
Value is: [ 3, Adam ]