Java · Theory

String Arrays in Java

Theory

57/270

String Arrays in Java

String Arrays is about Java arrays. An array is a fixed-size row of the same type. Index from 0. Length is a.length (a field, not a method). Last valid index is length - 1.

Create String Arrays: int[] a = new int[5]; or int[] a = {10, 20, 30};. A 2D array is an array of arrays: int[][] m = {{1,2},{3,4}}; m[1][0] is 3. Jagged means rows can have different lengths.

String Arrays size cannot grow. If you need grow/shrink, use ArrayList. Out of range → ArrayIndexOutOfBoundsException.

Let's take this on the board with one tiny Main class — no extra files. String Arrays in Java — prints length 3, middle value 20, then all values. Start from main, go line by line, and stop at each print. That output is the proof for String Arrays.

Diagram

index →  0    1    2
  array → [10,  20,  30]
           ↑         ↑
         first   length-1

Exam tip

Contrast array vs ArrayList in one line.

Example

// Array demo
public class Main {
  public static void main(String[] args) {
    int[] nums = {10, 20, 30};
    System.out.println(nums.length);
    System.out.println(nums[1]);
    for (int n : nums) System.out.print(n + " ");
  }
}

String Arrays in Java — prints length 3, middle value 20, then all values.

Short notes

DefString Arrays — array = fixed-size, same type, index from 0.
RuleString Arrays — a.length is a field. Last index = length - 1.
RememberString Arrays — 2D = array of arrays. Jagged = rows of different length.
TrapString Arrays — a[a.length] crashes. Size cannot grow — use ArrayList.

// Array demo public class Main { public static void main(String[] args) { int[] nums = {10, 20, 30}; System.out.println(nums.length); System.out.println(nums[1]); for (int n : nums) System.out.print(n + " "); } }

String Arrays in Java

Example

Short notes

Questions

String Arrays in Java

Example

Short notes

Questions