Top 10 Methods for Java Arrays

Category: Basics >> Top 10   September 12, 2013

The following are top 10 methods for Java Array. They are the most voted questions from stackoverflow.

0. Declare an array

String[] aArray = new String[5];
String[] bArray = {"a","b","c", "d", "e"};
String[] cArray = new String[]{"a","b","c","d","e"};

1. Print an array in Java

int[] intArray = { 1, 2, 3, 4, 5 };
String intArrayString = Arrays.toString(intArray);
 
// print directly will print reference value
System.out.println(intArray);
// [[email protected]
 
System.out.println(intArrayString);
// [1, 2, 3, 4, 5]

2. Create an ArrayList from an array

String[] stringArray = { "a", "b", "c", "d", "e" };
ArrayList<String> arrayList = new ArrayList<String>(Arrays.asList(stringArray));
System.out.println(arrayList);
// [a, b, c, d, e]

3. Check if an array contains a certain value

String[] stringArray = { "a", "b", "c", "d", "e" };
boolean b = Arrays.asList(stringArray).contains("a");
System.out.println(b);
// true

4. Concatenate two arrays

int[] intArray = { 1, 2, 3, 4, 5 };
int[] intArray2 = { 6, 7, 8, 9, 10 };
// Apache Commons Lang library
int[] combinedIntArray = ArrayUtils.addAll(intArray, intArray2);

5. Declare an array inline

method(new String[]{"a", "b", "c", "d", "e"});

6. Joins the elements of the provided array into a single String

// containing the provided list of elements
// Apache common lang
String j = StringUtils.join(new String[] { "a", "b", "c" }, ", ");
System.out.println(j);
// a, b, c

7. Covnert an ArrayList to an array

String[] stringArray = { "a", "b", "c", "d", "e" };
ArrayList<String> arrayList = new ArrayList<String>(Arrays.asList(stringArray));
String[] stringArr = new String[arrayList.size()];
arrayList.toArray(stringArr);
for (String s : stringArr)
	System.out.println(s);

8. Convert an array to a set

Set<String> set = new HashSet<String>(Arrays.asList(stringArray));
System.out.println(set);
//[d, e, b, c, a]

9. Reverse an array 

int[] intArray = { 1, 2, 3, 4, 5 };
ArrayUtils.reverse(intArray);
System.out.println(Arrays.toString(intArray));
//[5, 4, 3, 2, 1]

10. Remove element of an array

int[] intArray = { 1, 2, 3, 4, 5 };
int[] removed = ArrayUtils.removeElement(intArray, 3);//create a new array
System.out.println(Arrays.toString(removed));

One more - convert int to byte array 

byte[] bytes = ByteBuffer.allocate(4).putInt(8).array();
 
for (byte t : bytes) {
   System.out.format("0x%x ", t);
}

Related posts:

  1. Example of Sorting Arrays
  2. Read bytes from FileInputStream in Java
  3. Print an Array in Java
  4. Deep Understanding of Arrays.sort()
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  • Ojas Modi

    You need to add jar file of org.apache.common.lang3 in your runtime environment.

  • Glenn Li

    it says package does not exist

  • whitepower88

    get cacner nigag XDXD

  • Eduardo Montes

    You have to use: import org.apache.commons.lang3.ArrayUtils;

  • David Alvarez

    I’m unable to compile and run “ArrayUtils.reverse(intArray);”

  • Marshall Schaffer

    BTW, there is an “obvious” typo.:

    7. Covnert

    should be “Convert”

  • Marshall Schaffer

    BTW, there is an “obvious” typo.:

    7. Covnert

    should be “Convert”

    It’s not a big deal to me. The rest of the article was helpful. Thanks.

  • this is good post and help me more to understand java array. must visit java array program examples

  • petrovi4

    УОТ ТАК УОТ

  • ryanlr

    This is a good point. (3.) does not work for int type. “the problem lies in the interpretation of the varargs method Arrays.asList. It interprets the type to be int[], so that you receive back a List, not a List. So none of the numbers you pass in will be equal to an int[].”http://stackoverflow.com/questions/21197930/arrays-aslistan-array-containsan-integer-always-false-why

  • sdfghjkl

    sdfghjkl;’

  • Deva

    You can find the more details and the Example program here,

    http://javadomain.in/converting-string-array-integer-array-example-java/

  • Georgi Koemdzhiev

    These are good, but what about int array instead of String?? (3.)

  • danyal

    that was good but this will also be helpful : kodingexamples.blogspot.com/2014/04/how-to-reverse-string-in-java.html

  • Abhi

    Superb 😉
    I loved it a lot.