Arrays in Mercury

Our first example demonstrates the use of arrays in Java. In Java, an array is a fixed-size collection of elements of the same type.

public class Arrays {
    public static void main(String[] args) {
        // Here we create an array 'a' that will hold exactly 5 integers.
        // By default, an array is initialized with zeros for numeric types.
        int[] a = new int[5];
        System.out.println("emp: " + java.util.Arrays.toString(a));

        // We can set a value at an index using the array[index] = value syntax,
        // and get a value with array[index].
        a[4] = 100;
        System.out.println("set: " + java.util.Arrays.toString(a));
        System.out.println("get: " + a[4]);

        // The length property returns the length of an array.
        System.out.println("len: " + a.length);

        // Use this syntax to declare and initialize an array in one line.
        int[] b = {1, 2, 3, 4, 5};
        System.out.println("dcl: " + java.util.Arrays.toString(b));

        // In Java, we can't use the ... syntax to let the compiler count elements.
        // We need to explicitly specify the size or provide all elements.

        // If you want to create an array with specific indices set,
        // you'll need to do it manually in Java.
        int[] c = new int[5];
        c[0] = 100;
        c[3] = 400;
        c[4] = 500;
        System.out.println("idx: " + java.util.Arrays.toString(c));

        // Array types are one-dimensional, but you can create multi-dimensional
        // arrays by creating arrays of arrays.
        int[][] twoD = new int[2][3];
        for (int i = 0; i < 2; i++) {
            for (int j = 0; j < 3; j++) {
                twoD[i][j] = i + j;
            }
        }
        System.out.println("2d: " + java.util.Arrays.deepToString(twoD));

        // You can create and initialize multi-dimensional arrays at once too.
        twoD = new int[][] {
            {1, 2, 3},
            {4, 5, 6}
        };
        System.out.println("2d: " + java.util.Arrays.deepToString(twoD));
    }
}

Note that arrays in Java are printed using Arrays.toString() for one-dimensional arrays and Arrays.deepToString() for multi-dimensional arrays.

To run this program, save it as Arrays.java, compile it with javac Arrays.java, and then run it with java Arrays. The output will be:

emp: [0, 0, 0, 0, 0]
set: [0, 0, 0, 0, 100]
get: 100
len: 5
dcl: [1, 2, 3, 4, 5]
idx: [100, 0, 0, 400, 500]
2d: [[0, 1, 2], [1, 2, 3]]
2d: [[1, 2, 3], [4, 5, 6]]

Java arrays are similar to those in many other languages, providing a way to store multiple elements of the same type in a contiguous block of memory. They have a fixed size once created, and their elements can be accessed using zero-based indexing.

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Arrays in Mercury