Traverse Through ArrayList in Forward Direction in Java

11 Dec, 2020
ArrayList is a part of the collection framework and is present in java.util package. It provides us with dynamic arrays in Java. The listIterator() method of java.util.ArrayList class is used to return a list iterator over the elements in this list (in a proper organized sequence). ArrayList can be traversed in the forward direction using multiple ways.
Example:
Input : ArrayList: [5, 6, 8, 10]
Output:
Value is : 5
Value is : 6
Value is : 8
Value is : 10
Approach 1: Using listIterator Method
Create a list iterator object of a given ArrayList.Use while loop with the condition as hasNext() method.If hasNext() method returns false, loop breaks.Else print the value using object.next() method.
Create a list iterator object of a given ArrayList.
Use while loop with the condition as hasNext() method.
If hasNext() method returns false, loop breaks.
Else print the value using object.next() method.
Example:
Java
// Traverse through ArrayList in// forward direction using Javaimport java.util.*;import java.io.*;  class GFG {    public static void main(String[] args)    {        ArrayList<Integer> alist = new ArrayList<>();          // adding element to arrlist        alist.add(5);        alist.add(6);        alist.add(8);        alist.add(10);          ListIterator<Integer> it = alist.listIterator();          while (it.hasNext()) {            System.out.println("Value is : " + it.next());        }    }}
Value is : 5
Value is : 6
Value is : 8
Value is : 10
Time Complexity: O(N), where N is the length of ArrayList.
Approach 2: Using For Loop
Print all the values in ArrayList using for loop. Size of ArrayList can be obtained using ArrayList.size() method and for accessing the element use ArrayList.get() method. 
Implementation:
Java
// Traverse through ArrayList in// forward direction using Javaimport java.util.*;import java.io.*;  class GFG {    public static void main(String[] args)    {        ArrayList<Integer> alist = new ArrayList<>();          // adding element to arrlist        alist.add(5);        alist.add(6);        alist.add(8);        alist.add(10);          for (int i = 0; i < alist.size(); i++)            System.out.println("Value is : "                               + alist.get(i));    }}
Value is : 5
Value is : 6
Value is : 8
Value is : 10
Time Complexity: O(N), where N is the length of ArrayList.
Approach 3: Using forEach Loop
Print all the values in ArrayList using for each loop.
Example:
Java
// Traverse through ArrayList in// forward direction using Javaimport java.util.*;import java.io.*;  class GFG {    public static void main(String[] args)    {        ArrayList<Integer> alist = new ArrayList<>();          // adding element to arrlist        alist.add(5);        alist.add(6);        alist.add(8);        alist.add(10);          for (Integer i : alist)            System.out.println("Value is : " + i);    }}
Value is : 5
Value is : 6
Value is : 8
Value is : 10
Time Complexity: O(N), where N is the length of ArrayList.
Approach 4: Using Lambda Function
Print all the values in ArrayList using the lambda function.
Example:
Java
// Traverse through ArrayList in// forward direction using Javaimport java.util.*;import java.io.*;  class GFG {    public static void main(String[] args)    {        ArrayList<Integer> alist = new ArrayList<>();          // adding element to arrlist        alist.add(5);        alist.add(6);        alist.add(8);        alist.add(10);        // lambda        alist.forEach(            i -> System.out.println("Value is : " + i));    }}
Value is : 5
Value is : 6
Value is : 8
Value is : 10
Time Complexity: O(N), where N is the length of ArrayList.
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