Top 10 Methods for Java Arrays

作者：X Wang

出处：http://www.programcreek.com/2013/09/top-10-methods-for-java-arrays/

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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); // [I@7150bd4d   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); }