A quick guide to print the hashmap values onto the console or log in various ways.
1. Overview
In this article, we'll learn how to print the values of HashMap in different ways in java and jdk 8.
2. Java Print Hashmap values using Map reference
This is a very simple option to display the key and values onto the console using System.out.println() statement.
Example 1:
In the below program, print the key and its values of the map.
package com.javaprogramto.collections.hashmap.print;
import java.util.HashMap;
import java.util.Map;
public class HashMapPrintExample1 {
public static void main(String[] args) {
Map<Integer, String> map = new HashMap<>();
map.put(1, "one");
map.put(2, "two");
map.put(3, "three");
System.out.println("map values : "+map);
}
}
Output:
map values : {1=one, 2=two, 3=three}
3. Java 8 Print Hashmap values using Iterator
Call the iterator() on the entrySet() method. entrySet() returns Entry<Integer, String> objects as Set.
Next, run forEachRemaining() method of Iterator from java 8.
Example 2:
package com.javaprogramto.collections.hashmap.print;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
public class HashMapPrintExample2 {
public static void main(String[] args) {
Map<Integer, String> map = new HashMap<>();
map.put(1, "one");
map.put(2, "two");
map.put(3, "three");
Iterator<Map.Entry<Integer, String>> it = map.entrySet().iterator();
it.forEachRemaining( entry -> System.out.println(entry.getKey() + " - "+entry.getValue()));
}
}
Output:
1 - one 2 - two 3 - three
4. Java Print Hashmap values using entrySet()
Get the Set of Entry object using Map.entrySet() method and then call foreach() method.
Example 3:
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
public class HashMapPrintExample3 {
public static void main(String[] args) {
Map<Integer, String> map = new HashMap<>();
map.put(1, "one");
map.put(2, "two");
map.put(3, "three");
Set<Map.Entry<Integer, String>> set = map.entrySet();
set.forEach(System.out::println);
}
}
Output:
1=one 2=two 3=three
5. Java Print Hashmap values using keySet()
Invoke keySet() method and loop it through for loop to print the values.
Example 4:
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
public class HashMapPrintExample4 {
public static void main(String[] args) {
Map<Integer, String> map = new HashMap<>();
map.put(1, "one");
map.put(2, "two");
map.put(3, "three");
Set<Integer> keys = map.keySet();
for(Integer key : keys) {
System.out.println(key+" - "+map.get(key));
}
}
}
Output:
1 - one 2 - two 3 - three
6. Java 8 Print Hashmap values using BiConsumer
Java 8 is added with the BiConsumer functional interface and pass the biconsumer to the forEach() method.
Example 5:
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import java.util.function.BiConsumer;
public class HashMapPrintExample5 {
public static void main(String[] args) {
Map<Integer, String> map = new HashMap<>();
map.put(1, "one");
map.put(2, "two");
map.put(3, "three");
BiConsumer<Integer, String> printBiConsumer = (key, value) -> System.out.println(key+" - "+value);
map.forEach(printBiConsumer);
}
}
Output is the same as the above section.
7. Conclusion
In this article, we've seen what are the different ways to print the hashmap values in java 8 and older versions.
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