Java: Remove and get a key-value mapping associated with the least key in a map

Last update on April 30 2023 12:55:21 (UTC/GMT +8 hours)

Java Collection, TreeMap Exercises: Exercise-19 with Solution

Write a Java program to remove and get a key-value mapping associated with the least key in a map.

Sample Solution:-

Java Code:

import java.util.*;
import java.util.Map.Entry;  
public class Example19 {  
         public static void main(String args[]) {

  // Create a tree map
  TreeMap < Integer, String > tree_map = new TreeMap < Integer, String > ();

  // Put elements to the map 
  tree_map.put(10, "Red");
  tree_map.put(20, "Green");
  tree_map.put(40, "Black");
  tree_map.put(50, "White");
  tree_map.put(60, "Pink");

  // polling first entry
  System.out.println("Value before poll: " + tree_map);
  System.out.println("Value returned: " + tree_map.pollFirstEntry());
  System.out.println("Value after poll: " + tree_map);
 }
}

Sample Output:

Value before poll: {10=Red, 20=Green, 40=Black, 50=White, 60=Pink}     
Value returned: 10=Red                                                 
Value after poll: {20=Green, 40=Black, 50=White, 60=Pink}

Java Code Editor:

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Java: Tips of the Day

Java Classes

A Java class is declared with the keywords public class along with a unique class name mirroring its file name. For example, in a file Hello.java in project helloworld:

package helloworld;

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

/**
 * @author seth
 * A GUI hello world.
 */

public class Hello {
        // this is an empty class
}

You can declare variables and functions inside a class. In Java, variables within a class are called fields.

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