Java 8 forEach examples

Table of Contents

Map:
List:

In this post, we will see improved way of iterating through map and list which are introduced in java 8.

Map:

Normal way of iterating HashMap before java 8:

package org.arpit.java2blog;

import java.util.HashMap;

public class HashMapIterationMap {

public static void main(String args[])

{

// HashMap with Country as key and capital as value

HashMap<String,String> countryCapitalMap=new HashMap<String,String>();

countryCapitalMap.put("India","Delhi");

countryCapitalMap.put("Japan","Tokyo");

countryCapitalMap.put("France","Paris");

countryCapitalMap.put("Russia","Moscow");

// Iterating Using keySet() and for each loop

System.out.println("Iterating Using keySet() and for each loop");

for (String countryKey:countryCapitalMap.keySet()) {

System.out.println("Country:"+ countryKey +" and Capital:"+countryCapitalMap.get(countryKey));

}

System.out.println("-----------------------------");

}

Improved way of iterating HashMap in java 8:

package org.arpit.java2blog;

import java.util.HashMap;

public class HashMapIterationMap {

public static void main(String args[])

{

// HashMap with Country as key and capital as value

HashMap<String,String> countryCapitalMap=new HashMap<String,String>();

countryCapitalMap.put("India","Delhi");

countryCapitalMap.put("Japan","Tokyo");

countryCapitalMap.put("France","Paris");

countryCapitalMap.put("Russia","Moscow");

// Iterating Using Java 8

System.out.println("Iterating Using Java 8");

System.out.println("-----------------------------");

countryCapitalMap.forEach((k,v)->System.out.println("Country:" + k + " Capital : " + v));

System.out.println("-----------------------------");

}

When you run above program, you will get below output:

Iterating Using Java 8
—————————–
Country:Japan Capital : Tokyo
Country:France Capital : Paris
Country:India Capital : Delhi
Country:Russia Capital : Moscow
—————————–

List:

Normal way of iterating list:

package org.arpit.java2blog;

import java.util.ArrayList;

public class IteratingArrayListMain {

public static void main(String[] args) {

ArrayList nameList=new ArrayList();//creating arraylist

nameList.add("Arpit");//adding object in arraylist

nameList.add("John");

nameList.add("Martin");

nameList.add("Adam");

// Iterating list using foreach loop

for(String name :nameList )

{

System.out.print(name+" ");

}

Iterating through list in java 8:

package org.arpit.java2blog;

import java.util.ArrayList;

public class IteratingArrayListMain {

public static void main(String[] args) {

ArrayList nameList=new ArrayList();//creating arraylist

nameList.add("Arpit");//adding object in arraylist

nameList.add("John");

nameList.add("Martin");

nameList.add("Adam");

// Iterating list using foreach method

nameList.forEach(n->System.out.print(n+" "));

}

forEach method internally use Consumer Object.You can read more about Java 8 Consumer interface.

Arpit John Martin Adam

[Fixed] Unable to obtain LocalDateTime from TemporalAccessor

Convert LocalDate to Instant in Java

Convert Instant to LocalDate in Java

Convert String to LocalDateTime in Java

Format LocalDateTime to String in Java

Java 8 – Find duplicate elements in Stream

How to format Instant to String in java

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Java 8 forEach examples