Arrays.sort

Learn sorting with Arrays.sort.

Sorting with Arrays.sort

In Java, the easiest way to sort an array from smallest to largest is the Arrays.sort method. It sorts the array in place: it does not return a new array, it rearranges the elements of the existing one.

int[] scores = {78, 92, 55};
Arrays.sort(scores);
// scores is now: {55, 78, 92}

The method orders the array in ascending order. For binary search, which you will see later, the array must be sorted first.

Sorting and binary search

Some methods require a sorted array. Arrays.binarySearch is one of them: for fast lookup it requires the array to be sorted.

If the array is not sorted, binarySearch may return a wrong result; that is why you call Arrays.sort first.

int[] nums = {4, 2, 7, 1};
Arrays.sort(nums);
int i = Arrays.binarySearch(nums, 4);
// i = 2

Sorting also moves the smallest and largest values to the ends of the array, which makes further processing easier.

Exercise Sort and print the scores

Sort the scores below from smallest to largest and print each one on its own line.

Show example solution

Arrays.sort(scores);
for (int s : scores) {
  System.out.println(s);
}

Test yourself

What happens after calling Arrays.sort(scores)?
```
int[] scores = {78, 92, 55};
Arrays.sort(scores);
```
- It causes a compile error because Arrays.sort rejects int[]
- The scores array stays unchanged and a sorted copy is returned
- A new int[] is returned and scores stays the same
- The scores array is sorted in place and returns no value
Show answer

The scores array is sorted in place and returns no value — Arrays.sort is a void method; it sorts the array in place.

Fill in the blank: sort the array

int[] nums = {9, 3, 7};
____;
System.out.println(nums[0]);

Show answer

int[] nums = {9, 3, 7};
Arrays.sort(nums);
System.out.println(nums[0]);

Match method to behavior

Arrays.sort(x)

Sorts the array in place
Arrays.toString(x)

Converts the array to text
Arrays.binarySearch(x, v)

Searches a value in a sorted array
Arrays.copyOf(x, n)

Takes a copy of the array

Next lesson: Arrays.toString

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