Array declaration and initialization

  • In one line
int[] arr = {1, 2, 3};  
  • In multiple lines
int[] arr = new int[3];  
arr[0] = 1;  
arr[1] = 2;  
arr[2] = 3;  

Array properties and methods

  • Get array length
int[] arr = {1, 2, 3};  
int N = arr.length;  
  • Clone an array
int[] arr = {1, 2, 3};  
int[] clonedArr = arr.clone();  
  • Array traversal
int[] arr = {1, 2, 3};  
for(int i = 0; i < arr.length; i++) {  
    System.out.println(arr[i]);
}
int[] arr = {1, 2, 3};  
for(int ele : arr) {  
    System.out.println(ele);
}

Array sorting

  • Sort an array in ascending order
int[] arr = {1, 2, 3};  
Arrays.sort(arr);  
  • Sort an array in descending order
int[] arr = {1, 2, 3};  
arr = Arrays.stream(arr).boxed().sorted(Comparator.reverseOrder()).mapToInt(Integer::intValue).toArray();  
Integer[] arr = {1, 2, 3};  
Arrays.sort(arr, Collections.reverseOrder());  

Conversion

  • Convert String array to int array
String[] strs = {"1", "2", "3"};  
int[] arr = Arrays.stream(strs).mapToInt(Integer::parseInt).toArray();  
  • String join int / long / float / double array
int[] arr = {1, 2, 3};  
String str = Arrays.stream(arr).mapToObj(String::valueOf).collect(Collectors.joining(","));  
  • Print array
int[] arr = {1, 2, 3};  
System.out.println(Arrays.toString(arr));  

Aggregation

  • Sum of an array
int[] arr = {1, 2, 3};  
int sum = Arrays.stream(arr).sum();  
Integer[] arr = {1, 2, 3};  
int sum = Arrays.stream(arr).mapToInt(Integer::intValue).sum();  
  • Average of an array
int[] arr = {1, 2, 3};  
double avg = Arrays.stream(arr).average().getAsDouble();  
  • Min of an array
int[] arr = {1, 2, 3};  
int min = Arrays.stream(arr).min().getAsInt();  
  • Max of an array
int[] arr = {1, 2, 3};  
int max = Arrays.stream(arr).max().getAsInt();  

Notes

  • Arrays.stream and Comparator.reverseOrder methods are defined in java.util package and available since Java 8
  • Collectors class is defined in java.util.stream package and available since Java 8