Java – Convert Array to ArrayList

By mkyong | May 2, 2019 | Viewed : 89

In Java, we can use new ArrayList<>(Arrays.asList(array)) to convert an Array into an ArrayList

ArrayExample1.java

package com.mkyong;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class ArrayExample1 {

    public static void main(String[] args) {

        String[] str = {"A", "B", "C"};

        List<String> list = new ArrayList<>(Arrays.asList(str));

        list.add("D");

        list.forEach(x -> System.out.println(x));

    }
}

Output

A
B
C
D

The Arrays.asList returns a fixed or unmodifiable list, if we modify the list, UnsupportedOperationException will be thrown.

	List<String> list = Arrays.asList(str); 				 // unmodifiable list

	list.add("D"); 		// java.lang.UnsupportedOperationException
	
	List<String> list2 = new ArrayList<>(Arrays.asList(str)); // modifiable list
	
	list2.add("D"); 	// ok

1. Java 8 Stream

ArrayExample2.java

package com.mkyong;

import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;

public class ArrayExample2 {

    public static void main(String[] args) {

        String[] str = {"A", "B", "C"};

        ArrayList<String> list1 = Stream.of(str).collect(Collectors.toCollection(ArrayList::new));
        list1.add("D");
        list1.forEach(x -> System.out.println(x));

        List<String> list2 = Stream.of(str).collect(Collectors.toList());
        list2.add("D");
        list2.forEach(x -> System.out.println(x));

    }
}

Output

A
B
C
D
A
B
C
D

2. Java 9 – List.of()

P.S List.of returns fixed or unmodifiable list

ArrayExample3.java

package com.mkyong;

import java.util.ArrayList;
import java.util.List;

public class ArrayExample3 {

    public static void main(String[] args) {

        String[] str = {"A", "B", "C"};

        // Java 9
        List<String> list = new ArrayList<>(List.of("A", "B", "C"));

        list.add("D");

        list.forEach(x -> System.out.println(x));

    }
}

Output

A
B
C
D

References

• Java List java.lang.UnsupportedOperationException
• Java 9 List.of

array convert java java 8 java 9

About the Author

mkyong

Founder of Mkyong.com, love Java and open source stuff. Follow him on Twitter, or befriend him on Facebook or Google Plus. If you like my tutorials, consider make a donation to these charities.

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