Arrays in Karel

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

public class ArraysExample {
    public static void main(String[] args) {
        // Here we create an array 'a' that will hold exactly 5 integers.
        // By default, an array is zero-valued, which for integers means 0s.
        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));

        // Java doesn't have a direct equivalent to Go's [...] syntax,
        // but you can achieve similar results with Arrays.copyOf
        b = java.util.Arrays.copyOf(b, b.length);
        System.out.println("cpy: " + java.util.Arrays.toString(b));

        // Java doesn't support specifying indexes in array initialization,
        // but you can achieve similar results with a separate step
        b = new int[5];
        b[0] = 100;
        b[3] = 400;
        b[4] = 500;
        System.out.println("idx: " + java.util.Arrays.toString(b));

        // Array types are one-dimensional, but you can
        // create multi-dimensional 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},
            {1, 2, 3}
        };
        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 ArraysExample.java, compile it with javac ArraysExample.java, and then run it with java ArraysExample. 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]
cpy: [1, 2, 3, 4, 5]
idx: [100, 0, 0, 400, 500]
2d: [[0, 1, 2], [1, 2, 3]]
2d: [[1, 2, 3], [1, 2, 3]]

This example demonstrates basic array operations in Java, including creation, initialization, accessing elements, and working with multi-dimensional arrays.

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