How to Iterate Over Values in a Map in Java - Step by Step Examples

How to Iterate Over Values in a Map in Java ?

Answer

To iterate over values in a map in Java, you can use a for-each loop with the values method or an iterator. This allows you to access each value in the map.

✐ Examples

1 Iterating Over Values Using for-each Loop

We can iterate over values in a map in Java using a for-each loop with the values method, which provides a convenient syntax for iterating over all values in the map.

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 values method to get a collection of the values in the map.
We iterate over the values using a for-each loop, accessing each value directly from the collection.
We print each value to the console using the System.out.println function to verify that we are iterating over all values.

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");

        // Iterate over values using for-each loop
        for (String value : myMap.values()) {
            System.out.println(value);
        }
    }
}

Output

one
two
three

2 Iterating Over Values Using Iterator

We can iterate over values in a map in Java using an iterator, which provides a flexible way to access each value in the map.

For example,

We start by importing the java.util.HashMap and java.util.Iterator packages, which provide the HashMap and Iterator classes needed to create and manipulate the map and iterate over its values.
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 for the collection of values in the map using the values and iterator methods.
We use a while loop to iterate over the values of the map by incrementing the iterator. We access each value using the next method of the iterator.
We print each value to the console using the System.out.println function to verify that we are iterating over all values.

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");

        // Declare an iterator for the collection of values in the map
        Iterator<String> iterator = myMap.values().iterator();

        // Iterate over values using iterator
        while (iterator.hasNext()) {
            String value = iterator.next();
            System.out.println(value);
        }
    }
}

Output

one
two
three

3 Storing and Iterating Over Values Separately

We can store values in a separate list and then iterate over the list in Java, which provides a way to work with values independently of their keys.

For example,

We start by importing the java.util.HashMap and java.util.ArrayList packages, which provide the HashMap and ArrayList classes needed to create and manipulate the map and store the values.
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 a list named values to store the values from the map.
We use the values method to get a collection of the values in the map and add each value to the values list using the addAll method.
We use a for-each loop to iterate over the values list and print each value to the console using the System.out.println function to verify that we have stored all values separately.

Java Program

import java.util.HashMap;
import java.util.ArrayList;
import java.util.List;
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");

        // Declare a list to store the values
        List<String> values = new ArrayList<>();

        // Store values in the list
        values.addAll(myMap.values());

        // Iterate over the values list
        for (String value : values) {
            System.out.println(value);
        }
    }
}

Output

one
two
three

Summary

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

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How to Iterate Over Values in a Map in Java - Step by Step Examples