Java .length

In Java, the .length property is used to determine the length or size of an array. It is a built-in property for arrays and returns an integer value that represents the number of elements in the array. Understanding how to use .length is crucial for iterating through arrays, avoiding out-of-bounds errors, and dynamically managing data.

Syntax

arrayName.length;

Parameters:

• arrayName: The name of the array to call .length on.

Return Value:

The .length property returns an integer value that represents the number of elements in the array.

Example 1: Basic Usage of .length

This example uses the .length property to determine the array length:

public class Array {
  public static void main(String[] args) {
    // Create an array
    String[] colors = {"Violet", "Indigo", "Blue", "Green", "Yellow", "Orange", "Red"};

    // Find the size of the array
    int length = colors.length;

    // Print the result
    System.out.println("The length of the array is: " + length);
  }
}

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Since the colors array contains 7 elements, the output for the example will be:

The length of the array is: 7

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Example 2: Using .length for Looping Through an Array

This example uses the .length property for looping through an array and printing the elements in it:

public class Loop {
  public static void main(String[] args) {
    // Create an array
    String[] fruits = {"Apple", "Banana", "Cherry"};

    // Loop through the array and print the elements in it
    for (int i = 0; i < fruits.length; i++) {
      System.out.println(fruits[i]);
    }
  }
}

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The output for the example will be:

Apple
Banana
Cherry

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Example 3: Using .length with Multi-Dimensional Arrays

This example uses the .length property to determine the number of rows and number of columns in the first row of a multi-dimensional array:

public class MultiDimensionalArray {
  public static void main(String[] args) {
    // Create a multi-dimensional array
    int[][] numbers = {
      {1, 2, 3},
      {4, 5, 6},
      {7, 8, 9}
    };

    // Print the number of rows in the array
    System.out.println("The number of rows in the array: " + numbers.length);

    // Print the number of columns in the first row of the array
    System.out.println("The number of columns in the first row of the array: " + numbers[0].length);
  }
}

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The output for the example will be:

The number of rows in the array: 3
The number of columns in the first row of the array: 3

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Frequently Asked Questions

1. What is the difference between .length and .length()?

.length is an array property, whereas .length() is a string method.

2. Can the length of an array be changed?

No. Once an array is created, its length is constant and cannot be changed. To work with dynamic sizes, consider using ArrayList.

3. What happens if I access an index beyond the array’s length?

You’ll get an ArrayIndexOutOfBoundsException error, which is a runtime error.