How to Print a Map in Java - Step by Step Examples

How to Print a Map in Java ?

Answer

To print a map in Java, you can iterate over the map using a for-each loop, an iterator, or the forEach method to print each key-value pair.

✐ Examples

1 Printing a Map Using For-Each Loop

We can print a map in Java by iterating over the map using a for-each loop and printing each key-value pair.

For example,

We start by importing the java.util.HashMap package, which provides the HashMap class needed to create and manipulate the map.
We declare and initialize a map named myMap with some key-value pairs. In this example, the map has integer keys and string values.
We use a for-each loop to iterate over the entry set of the map. The loop variable entry represents each key-value pair in the map as a Map.Entry object.
Inside the loop, we print the key and value of each pair using System.out.println.

Java Program

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

public class Main {
    public static void main(String[] args) {
        // Declare and initialize a map
        Map<Integer, String> myMap = new HashMap<>();
        myMap.put(1, "one");
        myMap.put(2, "two");
        myMap.put(3, "three");

        // Print the map using for-each loop
        for (Map.Entry<Integer, String> entry : myMap.entrySet()) {
            System.out.println(entry.getKey() + ": " + entry.getValue());
        }
    }
}

Output

1: one
2: two
3: three

2 Printing a Map Using Iterator

We can print a map in Java by iterating over the map using an iterator and printing each key-value pair.

For example,

We start by importing the java.util.HashMap and java.util.Iterator packages, which provide the HashMap class and iterator interface needed to create and manipulate the map.
We declare and initialize a map named myMap with some key-value pairs. In this example, the map has integer keys and string values.
We declare an iterator of type Iterator<Map.Entry<Integer, String>> and initialize it to the entry set of the map using the iterator() method.
We use a while loop to iterate over the map entries until the iterator reaches the end of the map. Inside the loop, we print the key and value of each pair using System.out.println and move the iterator to the next pair using the next() method.

Java Program

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

public class Main {
    public static void main(String[] args) {
        // Declare and initialize a map
        Map<Integer, String> myMap = new HashMap<>();
        myMap.put(1, "one");
        myMap.put(2, "two");
        myMap.put(3, "three");

        // Print the map using iterator
        Iterator<Map.Entry<Integer, String>> iterator = myMap.entrySet().iterator();
        while (iterator.hasNext()) {
            Map.Entry<Integer, String> entry = iterator.next();
            System.out.println(entry.getKey() + ": " + entry.getValue());
        }
    }
}

Output

1: one
2: two
3: three

3 Printing a Map Using forEach Method

We can print a map in Java by iterating over the map using the forEach method and printing each key-value pair.

For example,

We start by importing the java.util.HashMap package, which provides the HashMap class needed to create and manipulate the map.
We declare and initialize a map named myMap with some key-value pairs. In this example, the map has integer keys and string values.
We use the forEach method to iterate over the map. The forEach method takes a lambda expression that defines the operation to be performed on each element.
The lambda expression takes two parameters: key and value. Inside the lambda expression, we print the key and value of each pair using System.out.println.

Java Program

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

public class Main {
    public static void main(String[] args) {
        // Declare and initialize a map
        Map<Integer, String> myMap = new HashMap<>();
        myMap.put(1, "one");
        myMap.put(2, "two");
        myMap.put(3, "three");

        // Print the map using forEach method
        myMap.forEach((key, value) -> System.out.println(key + ": " + value));
    }
}

Output

1: one
2: two
3: three

Summary

In this tutorial, we learned How to Print a Map in Java language with well detailed examples.

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How to Print a Map in Java - Step by Step Examples