Sunday, 28 June 2015

How to Convert an Array to ArrayList In Java ?

    Using Arrays.asList() method you can convert the given array to ArrayList in java. Let's see an example. The implementation of asList() method is like below in java.

 public static <T> List<T> asList(T... a) {
    return new ArrayList<T>(a);
 }
 

The Program is

package com.speakingcs.collections;

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

public class ArrayToArrayList {

    /**
     * @param args
     */
    public static void main(String[] args) {
        
        String[] strArr = {"abc","bcd","cde","def","efg","fgh","ghi","hij","ijk"};
        convertToArrayList(strArr);

    }
    
    
    public static void convertToArrayList(String[] strArr) {
        List<String> aList = Arrays.asList(strArr);
        
        for(String str: aList) {
            System.out.println(str);
        }
        
        aList.add("jkl");
        aList.add("klm");
    }

}
 
Points To Note:

1. Performing adding of an element to the returned ArrayList, results an exception - java.lang.UnsupportedOperationException.
aList.get(0);


2. Performing removing of an element to the returned ArrayList also results an UnsupportedOperationException - java.lang.UnsupportedOperationException.
 aList.remove("abc");

3. You can perform other operations such  as - get(), contains(), indexOf() - as these are read only operations on the list and won't cause any structural change.
aList.indexOf("abc");
aList.contains("abc");


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