Java Array Fundamentals: Syntax, Indexing, and Code Examples

Posted on Oct 11, 2025 in Computer Engineering

Java Array Fundamentals: Core Concepts and Syntax

Array Properties and Declaration

Fixed Size Property

Once an array is created, its size is fixed.

Valid Array Declarations (int values)

Which of the following are correct ways to declare an array of int values?

  • int[] a;
  • int a[];

Valid Array Declarations (Mixed Types)

Which of the following statements are valid?

  • double d[] = new double[30];
  • int[] i = {3, 4, 3, 2};

Incorrect Array Declarations and Initializations

Which of the following declarations or initializations are incorrect?

  1. int[] a = new int(2); (Incorrect: Use brackets [] for size.)
  2. int a = new int[2]; (Incorrect: Type mismatch; a is int, not int[].)
  3. int a() = new int[2]; (Incorrect: Syntax error.)

Character Array Initialization Methods

How can you initialize an array of two characters to ‘a’ and ‘b’?

Both methods below are valid:

  • char[] charArray = {'a', 'b'};
  • char[] charArray = new char[2]; charArray[0] = 'a'; charArray[1] = 'b';

Array Size and Indexing

Determining Array Bounds

If you declare an array double[] list = new double[5]:

  • How many elements are in the array? 5
  • The highest index in array list is 4.

Accessing Elements by Index

If you declare an array double[] list = {3.4, 2.0, 3.5, 5.5}, what is list[1]?

Answer: 2.0

Code Analysis: Array Manipulation and Errors

Finding the Index of the Maximum Value

Analyze the following code snippet designed to find the index of the maximum element. What is the output?

double[] myList = {1, 5, 5, 5, 5, 1};
double max = myList[0];
int indexOfMax = 0;
for (int i = 1; i < myList.length; i++) {
    if (myList[i] > max) {
        max = myList[i];
        indexOfMax = i;
    }
}
System.out.println(indexOfMax);

Output: 1 (The code finds the index of the first occurrence of the maximum value.)

Runtime Error: ArrayIndexOutOfBoundsException

Analyze the following code:

public class Test {
    public static void main(String[] args) {
        int[] x = new int[5];
        int i;
        for (i = 0; i < x.length; i++)
            x[i] = i;
        System.out.println(x[i]);
    }
}

Result: The program has a runtime error because the last statement System.out.println(x[i]); causes an ArrayIndexOutOfBoundsException. The loop terminates when i equals 5, which is outside the valid index range [0, 4].

Enhanced For Loop Output

Analyze the following code using an enhanced for loop:

public class Test {
    public static void main(String[] args) {
        double[] x = {2.5, 3, 4};
        for (double value: x)
            System.out.print(value + " ");
    }
}

Output: The program displays 2.5 3.0 4.0.

Array Shifting and Value Propagation

What is the output of the following code?

public class Test {
    public static void main(String[] args) {
        int list[] = {1, 2, 3, 4, 5, 6};
        for (int i = 1; i < list.length; i++)
            list[i] = list[i - 1];
        for (int i = 0; i < list.length; i++)
            System.out.print(list[i] + " ");
    }
}

Output: 1 1 1 1 1 1

Reference Assignment and Shared Memory

In the following code, what is the output for list2?

public class Test {
    public static void main(String[] args) {
        int[] list1 = {1, 2, 3};
        int[] list2 = {1, 2, 3};
        list2 = list1; // list2 now points to the same array as list1
        list1[0] = 0;
        list1[1] = 1;
        list2[2] = 2; // Modifies the shared array
        for (int i = 0; i < list2.length; i++)
            System.out.print(list2[i] + " ");
    }
}

Output: 0 1 2

The Final Keyword and Array References

Analyze the following code:

public class Test {
    public static void main(String[] args) {
        final int[] x = {1, 2, 3, 4};
        int[] y = x;
        x = new int[2]; // Attempt to reassign the final reference x
        for (int i = 0; i < y.length; i++)
            System.out.print(y[i] + " ");
    }
}

Result: The program has a compile error on the statement x = new int[2], because x is declared as final and its reference cannot be changed.

Miscellaneous Code Observations

Unidentified Code Output 1

What is the output of the following code? int 2 3 4 5 6 1.

(Note: This is a standalone output fragment, possibly resulting from an array rotation operation.)

Unidentified Code Output 2

Analyze the following code: The program displays 1 2 3 4.

Fragmented Code Snippet

Analyze the following code. public (int)(Math.random() * 100)) c). i + 10 |

(This snippet is highly fragmented and lacks context, likely related to generating random array values.)