10 commonly used methods for java arrays

Create an array:

String[] a = new String[5];
String[] b = {“a”,”b”,”c”, “d”, “e”};
String[] c = new String[]{“a”,”b”,”c”,”d”,”e”};

1. Print the array

We often use for loops or some iterators to print out all elements of the array. But we can also change the posture.

int array[] = {1,2,3,4,5};
System.out.println(array); //[I@1234be4e
String arrStr = Arrays.toString(array);
System.out.println(array); //[1,2,3,4,5];

2. Create ArrayList

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

3. Check whether it contains a certain value

int array[] = {1,2,3,4,5};
boolean isContain= Arrays.asList(array).contains(5);
System.out.println(isContain);
// true

4. Connect two arrays

int[] array1 = { 1, 2, 3, 4, 5 };
int[] array2 = { 6, 7, 8, 9, 10 };
// Apache Commons Lang library
int[] combinedIntArray = ArrayUtils.addAll(array1, array2);

5. In one line Declare an array

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

6, invert the array

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

7, delete an element

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

8, convert it to set

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

9, convert Array Convert List to 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);

10. Compose array elements into a string

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

For more related knowledge, please pay attention tojava basic tutorialcolumn

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