In this article, we will see “How to iterate a Map and a List using forEach statement in Java 8”. Here, we will go through several examples to understand this feature.
Iterate Map & List using Java 8 forEach...!!! Share on X
Example 1. Map with forEach
import java.util.HashMap;
import java.util.Map;
import java.util.function.BiConsumer;
public class ForEach_Java8_Map_Example {
public static void main(String[] args) {
Map < Integer, String > map = new HashMap < Integer, String > ();
map.put(65, "noni");
map.put(33, "yogi");
map.put(73, "dv");
map.put(46, "pulkit");
map.put(37, "isha");
map.put(98, "yashi");
map.put(54, "yashu");
System.out.println("forEach Anonymous Class Implementation:\n");
map.forEach(new BiConsumer < Integer, String > () {
@Override
public void accept(Integer k, String v) {
System.out.println("Key: " + k + " Value: " + v);
}
});
System.out.println("\nforEach Lambda Implementation:\n");
map.forEach((k, v) - > System.out.println("Key: " + k + " Value: " + v));
}
}
Output:
forEach Anonymous Class Implementation: Key: 65 Value: noni Key: 33 Value: yogi Key: 98 Value: yashi Key: 37 Value: isha Key: 54 Value: yashu Key: 73 Value: dv Key: 46 Value: pulkit forEach Lambda Implementation: Key: 65 Value: noni Key: 33 Value: yogi Key: 98 Value: yashi Key: 37 Value: isha Key: 54 Value: yashu Key: 73 Value: dv Key: 46 Value: pulkit
Example 2. Map with forEach (conditional)
import java.util.HashMap;
import java.util.Map;
public class ForEach_Java8_Map_Conditional_Example {
public static void main(String[] args) {
Map < Integer, String > users = new HashMap < Integer, String > ();
users.put(65, "noni");
users.put(33, "yogi");
users.put(73, "dv");
users.put(46, "pulkit");
users.put(37, "isha");
users.put(98, "yashi");
users.put(54, "yashu");
//Map Conditional check
System.out.println("Print users whose name starts with 'y' :\n");
users.forEach((id, name) - > {
if (name.startsWith("y")) {
System.out.println("Key: " + id + " Value: " + name);
}
});
}
}
Output:
Print users whose name starts with 'y' : Key: 33 Value: yogi Key: 98 Value: yashi Key: 54 Value: yashu
Example 3. List with forEach
import java.util.ArrayList;
import java.util.List;
import java.util.function.Consumer;
public class ForEach_Java8_List_Example {
public static void main(String[] args) {
List < String > users = new ArrayList < String > ();
users.add("noni");
users.add("yogi");
users.add("dv");
users.add("pulkit");
users.add("isha");
users.add("yashi");
users.add("yashu");
//Anonymous Class Implementation
System.out.println("forEach Anonymous Class Implementation:\n");
users.forEach(new Consumer < String > () {
@Override
public void accept(String v) {
System.out.println("List user names: " + v);
}
});
//Lambda Implementation
System.out.println("\nforEach Lambda Implementation:\n");
users.forEach((v) - > System.out.println("List user names: " + v));
//Java 8 Method Reference
System.out.println("\nJava 8 Method Reference Implementation:\n");
System.out.println("List user names: \n");
users.forEach(System.out::println);
//Java 8 Stream Implementation
System.out.println("\nJava 8 Stream Implementation Implementation:\n");
users.stream().forEach((v) - > System.out.println("List user names: " + v));
}
}
Output:
forEach Anonymous Class Implementation: List user names: noni List user names: yogi List user names: dv List user names: pulkit List user names: isha List user names: yashi List user names: yashu forEach Lambda Implementation: List user names: noni List user names: yogi List user names: dv List user names: pulkit List user names: isha List user names: yashi List user names: yashu Java 8 Method Reference Implementation: List user names: noni yogi dv pulkit isha yashi yashu Java 8 Stream Implementation Implementation: List user names: noni List user names: yogi List user names: dv List user names: pulkit List user names: isha List user names: yashi List user names: yashu
Example 4. List with forEach (conditional)
import java.util.ArrayList;
import java.util.List;
public class ForEach_Java8_List_Conditional_Example4 {
public static void main(String[] args) {
List < String > users = new ArrayList < String > ();
users.add("noni");
users.add("yogi");
users.add("dv");
users.add("pulkit");
users.add("isha");
users.add("yashi");
users.add("yashu");
//List Conditional check
System.out.println("Check the list if contains the user with name 'pulkit':\n");
users.forEach((name) - > {
if (name.equals("pulkit")) {
System.out.println("Expected name 'pulkit' is present in the list");
}
});
}
}
Output:
Check the list if contains the user with name 'Tommy': Expected name 'pulkit' is present in the list
Iterate Map & List using Java 8 forEach...!!! Share on X
Do you like this Post? – then check my other helpful posts:
- Double the even / odd numbers of a specified ArrayList using Streams
- Double the numbers of specified ArrayList using Streams
