Slices in Mercury

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class Slices {
    public static void main(String[] args) {
        // In Java, we use ArrayList as a dynamic array equivalent to Go's slices
        // An uninitialized ArrayList is empty but not null
        ArrayList<String> s = new ArrayList<>();
        System.out.println("uninit: " + s + " " + s.isEmpty() + " " + (s.size() == 0));

        // To create an empty ArrayList with non-zero capacity, we can use the constructor
        s = new ArrayList<>(3);
        System.out.println("emp: " + s + " len: " + s.size() + " cap: " + ((ArrayList<String>) s).ensureCapacity(3));

        // We can add and get elements just like with arrays
        s.add("a");
        s.add("b");
        s.add("c");
        System.out.println("set: " + s);
        System.out.println("get: " + s.get(2));

        // size() returns the length of the ArrayList
        System.out.println("len: " + s.size());

        // We can add more elements to the ArrayList
        s.add("d");
        s.addAll(Arrays.asList("e", "f"));
        System.out.println("apd: " + s);

        // We can create a copy of an ArrayList
        ArrayList<String> c = new ArrayList<>(s);
        System.out.println("cpy: " + c);

        // Sublist in Java is similar to slice in Go
        List<String> l = s.subList(2, 5);
        System.out.println("sl1: " + l);

        l = s.subList(0, 5);
        System.out.println("sl2: " + l);

        l = s.subList(2, s.size());
        System.out.println("sl3: " + l);

        // We can declare and initialize an ArrayList in a single line
        ArrayList<String> t = new ArrayList<>(Arrays.asList("g", "h", "i"));
        System.out.println("dcl: " + t);

        // Java doesn't have a built-in slices package, but we can compare ArrayLists
        ArrayList<String> t2 = new ArrayList<>(Arrays.asList("g", "h", "i"));
        if (t.equals(t2)) {
            System.out.println("t == t2");
        }

        // Multi-dimensional ArrayLists
        ArrayList<ArrayList<Integer>> twoD = new ArrayList<>();
        for (int i = 0; i < 3; i++) {
            twoD.add(new ArrayList<>());
            for (int j = 0; j <= i; j++) {
                twoD.get(i).add(i + j);
            }
        }
        System.out.println("2d: " + twoD);
    }
}

Unlike Go’s slices, Java uses ArrayList as a dynamic array. ArrayList provides similar functionality to Go’s slices, but with some differences in syntax and available methods.

To run the program, save it as Slices.java and use javac to compile and java to run:

$ javac Slices.java
$ java Slices
uninit: [] true true
emp: [] len: 0 cap: 3
set: [a, b, c]
get: c
len: 3
apd: [a, b, c, d, e, f]
cpy: [a, b, c, d, e, f]
sl1: [c, d, e]
sl2: [a, b, c, d, e]
sl3: [c, d, e, f]
dcl: [g, h, i]
t == t2
2d: [[0], [1, 2], [2, 3, 4]]

Note that while ArrayList in Java provides similar functionality to slices in Go, there are some differences:

Java uses ArrayList instead of built-in slice syntax.
Capacity in Java’s ArrayList is managed internally and not directly accessible.
Slicing in Java is done using the subList method, which returns a view of the original list.
Java doesn’t have a built-in slices package, but ArrayList provides methods for comparison and manipulation.

Despite these differences, ArrayList in Java can be used to achieve similar functionality to Go’s slices in most cases.

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Slices in Mercury