Common array operations in Java - Cheat Sheet & Quick Revision

overview

Recall & Review

beginner

What is the syntax to declare and initialize an array of integers with values 1, 2, 3 in Java?

You can declare and initialize an integer array like this:

int[] numbers = {1, 2, 3};

beginner

How do you find the length of an array named arr in Java?

Use arr.length to get the number of elements in the array.
Example:

int size = arr.length;

beginner

How can you loop through all elements of an array arr using a for-each loop?

Use the for-each loop syntax:

for (int element : arr) {
    // use element
}

This goes through each item in arr one by one.

intermediate

How do you copy an array source to a new array copy in Java?

You can use Arrays.copyOf:

int[] copy = Arrays.copyOf(source, source.length);

This creates a new array with the same elements.

beginner

How do you sort an array arr of integers in Java?

Use Arrays.sort(arr); to sort the array in ascending order.
Example:

Arrays.sort(arr);

Which of the following is the correct way to declare an array of strings named names?

A String[] names = new String;

B String[] names;

C String names = new String[];

D String names[] = ();

How do you access the third element of an array arr?

A arr.get(3)

B arr[3]

C arr[2]

D arr(2)

What does arr.length return?

A The number of elements in the array

B The last element of the array

C The size of the array in bytes

D The index of the last element

Which method sorts an array arr in Java?

A Arrays.sort(arr);

B arr.sort();

C Collections.sort(arr);

D arr.sorted();

How do you loop through all elements of an array arr using a for-each loop?

A for each (int x in arr) { }

B for (int i = 0; i < arr.length; i++) { }

C for (int i = 1; i <= arr.length; i++) { }

D for (int x : arr) { }

Explain how to declare, initialize, and access elements in a Java array.

Describe how to loop through all elements of an array and how to sort an array in Java.