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ArrayList forEach() method in Java

  • Difficulty Level : Basic
  • Last Updated : 26 Nov, 2018
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The forEach() method of ArrayList used to perform the certain operation for each element in ArrayList. This method traverses each element of the Iterable of ArrayList until all elements have been Processed by the method or an exception is raised. The operation is performed in the order of iteration if that order is specified by the method. Exceptions thrown by the Operation are passed to the caller.

Until and unless an overriding class has specified a concurrent modification policy, the operation cannot modify the underlying source of elements so we can say that behavior of this method is unspecified.

Retrieving Elements from Collection in Java.

Syntax:

public void forEach(Consumer<? super E> action)

Parameter: This method takes a parameter action which represents the action to be performed for each element.



Returns: This method does not returns anything.

Exception: This method throws NullPointerException if the specified action is null.

Below programs illustrate forEach() method of ArrayList:

Program 1: Program to demonstrate forEach() method on ArrayList which contains a list of Numbers.




// Java Program Demonstrate forEach()
// method of ArrayList
  
import java.util.*;
public class GFG {
  
    public static void main(String[] args)
    {
        // create an ArrayList which going to
        // contains a list of Numbers
        ArrayList<Integer> Numbers = new ArrayList<Integer>();
  
        // Add Number to list
        Numbers.add(23);
        Numbers.add(32);
        Numbers.add(45);
        Numbers.add(63);
  
        // forEach method of ArrayList and
        // print numbers
        Numbers.forEach((n) -> System.out.println(n));
    }
}
Output:
23
32
45
63

Program 2: Program to demonstrate forEach() method on ArrayList which contains list of Students Names.




// Java Program Demonstrate forEach()
// method of ArrayList
  
import java.util.*;
public class GFG {
  
    public static void main(String[] args)
    {
        // create an ArrayList which going to
        // contains a list of Student names which is actually
        // string values
        ArrayList<String> students = new ArrayList<String>();
  
        // Add Strings to list
        // each string represents student name
        students.add("Ram");
        students.add("Mohan");
        students.add("Sohan");
        students.add("Rabi");
  
        // print result
        System.out.println("list of Students:");
  
        // forEach method of ArrayList and
        // print student names
        students.forEach((n) -> print(n));
    }
  
    // printing student name
    public static void print(String n)
    {
        System.out.println("Student Name is " + n);
    }
}
Output:
list of Students:
Student Name is Ram
Student Name is Mohan
Student Name is Sohan
Student Name is Rabi

Reference: https://docs.oracle.com/javase/10/docs/api/java/util/ArrayList.html#forEach(java.util.function.Consumer)

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