How to initialize ArrayList in java
We have many ways to initialize ArrayList in java.
ArrayList can be initialized in one line, Using constructors, Using Arrays.
1. Initialize ArrayList using Constructors
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 | package com.kscodes.sampleproject; import java.util.ArrayList; import java.util.List; public class ArrayListInitalize { public static void main(String[] args) { List<String> arrList = new ArrayList<>(); arrList.add("Java"); arrList.add("JSP"); arrList.add("JavaScript"); arrList.add("JQuery"); System.out.println(arrList.toString()); } } |
2. Initialize ArrayList in One line using Arrays.asList()
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 | package com.kscodes.sampleproject; import java.util.ArrayList; import java.util.Arrays; import java.util.List; public class ArrayListInitalize { public static void main(String[] args) { List<String> arrList = new ArrayList<>(Arrays.asList("Java","JSP","JavaScript","JQuery")); System.out.println(arrList.toString()); } } |
3. Initialize ArrayList using Collections (Another List)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 | package com.kscodes.sampleproject; import java.util.ArrayList; import java.util.Arrays; import java.util.List; public class ArrayListInitalize { public static void main(String[] args) { List<String> arrList1 = new ArrayList<>(Arrays.asList("Java","JSP","JavaScript","JQuery")); List<String> arrList2 = new ArrayList<>(arrList1); System.out.println(arrList2.toString()); } } |
4. Initialize ArrayList using InnerClass
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 | package com.kscodes.sampleproject; import java.util.ArrayList; import java.util.List; public class ArrayListInitalize { public static void main(String[] args) { List<String> arrList = new ArrayList<String>(){{ add("Java"); add("JSP"); add("JavaScript"); add("JQuery"); } }; System.out.println(arrList.toString()); } } |
Reference
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