Array Basics
What is the index of the first element in a Java array?
0
What will this code output:
int[] arr = {1, 2, 3};
System.out.println(arr[1]);
2
What is the value of arr[2] in int[] arr = {10, 20, 30, 40}?
30
How do you create a 2D array of integers in Java?
int[][] arr = new int[3][4];
This term refers to a set of instructions that a computer follows to perform a task, and it is a core concept in software development.
Programming
How do you declare an array of integers in Java?
int[] arr = new int[5];
Write a loop to print all elements of the array:
int[] arr = {1, 2, 3, 4};
int[] arr = {1, 2, 3, 4};
for (int i = 0; i < arr.length; i++) {
System.out.println(arr[i]);
}
How would you change the value of the first element in an array?
array[0] = value;
Write a code snippet to access the element at the second row and third column of a 2D array.
int[][] arr = {
{1, 2, 3},
{4, 5, 6},
{7, 8, 9}
};
int element = arr[1][2]; // Access the element at row 2, column 3 (0-based index)
System.out.println(element); // Output will be 6
This control structure in Java evaluates a condition and executes one block of code if true, and another block if false.
IF statement
What is the size of the array int[] arr = {5, 10, 15, 20, 25}?
5
Write the code to find the sum of elements in an array.
int[] arr = {1, 2, 3};
int[] arr = {1, 2, 3};
int sum = 0;
for (int i = 0; i < arr.length; i++) {
sum += arr[i];
}
System.out.println(sum);
What is the result of this operation: arr[0] = arr[1] + arr[2] in int[] arr = {1, 2, 3}?
arr[0] becomes 5 (since 2 + 3 = 5).
How can you print all elements of a 2D array using nested loops ?
int[][] arr = {
{1, 2, 3},
{4, 5, 6},
{7, 8, 9}
};
for (int i = 0; i < arr.length; i++) { // Outer loop for rows
for (int j = 0; j < arr[i].length; j++) { // Inner loop for columns
System.out.print(arr[i][j] + " ");
}
System.out.println(); // Move to the next line after each row
}
This type of loop in Java will continue executing a block of code as long as a specified condition is true, often used when the number of iterations is not known in advance.
WHILE loop
What does arr[arr.length - 1] represent in an array?
last element in the array
Write a code to get the maximum element in an array.
int max = arr[0];
for (int i = 1; i < arr.length; i++) {
if (arr[i] > max) {
max = arr[i];
}
}
What happens when you try to access an index outside the bounds of an array?
It throws an ArrayIndexOutOfBoundsException.
What is the difference between a rectangular array and a jagged array?
Rectangular array: A 2D array where each row has the same number of columns. It is essentially a grid with uniform dimensions.
Jagged array: A 2D array where each row can have a different number of columns. It’s an array of arrays, where the sub-arrays can vary in length.
In Java, this special method is used to initialize an object when it is created, typically setting values for the object's attributes.
Constructor
Explain how array indexing works in Java.
Array indexing in Java starts at 0, meaning the first element is accessed with index 0.
Explain how nested loops work when traversing a 2D array.
The outer loop iterates over the rows, and the inner loop iterates over the elements (columns) in each row.
Write a code to double each element in an array.
for (int i = 0; i < arr.length; i++) { arr[i] *= 2; }
Write a code that computes the sum of all elements in a 2D array.
int sum = 0;
for (int i = 0; i < arr.length; i++) { // Iterate over rows
for (int j = 0; j < arr[i].length; j++) { // Iterate over columns
sum += arr[i][j];
}
}
This concept in Java allows a method to call itself, which can be especially useful in solving problems that can be broken down into smaller, similar subproblems.
Recursion