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
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 | 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:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 | 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)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 | 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:
1 2 3 4 5 | Print users whose name starts with 'y' : Key: 33 Value: yogi Key: 98 Value: yashi Key: 54 Value: yashu |
Example 3. List with forEach
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 | 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:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 | 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)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 | 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:
1 2 3 | 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
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