Java Basics

/*
 *  Point of this is to cover all the basics you will need to remember for the competition.
 *  Nothing challenging, just all the core stuff.
 */

import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.Scanner;



public class template {
    public static void main(String args[]){

        // Type syso then press ctrl+space to add the output line
        System.out.println("Hello world!");

        int x = 3;

        String s = "String";
        char c = 'c';
        float f = 1.2345f; // Need the f to explicitly create a float (32-bits precision)
        double d = 1.2345; // 64-bits
        boolean b = true;

        System.out.println("Output with variable concatenated: " + d);
        System.out.print("Output without new line added by default.\nNew line\n");

        // Object used to read input
        Scanner in = new Scanner(System.in);

        // Get an int
        System.out.print("Type in a number: ");
        int y = in.nextInt();
        // This clears the line. Essential this is used after reading anything in other than the whole line.
        in.nextLine();

        System.out.print("Type in a string: ");
        String str = in.nextLine(); // Use this to get the whole line.


        System.out.println("Number entered: " + y + ", string entered: \"" + str + "\"");

        System.out.print("Press enter to continue.");
        in.nextLine();


        // Arrays- type name[] = new type[size]
        // When you know the size
        int xs[] = new int[10];
        // When you don't know the size
        int ys[][];
        // Re-assigning a variable for multiple arrays of different sizes
        ys = new int[3][4];
        ys = new int[5][7];

        System.out.println("Filling array xs with values:");
        // Fill it with descending values
        for(int i=0;i<xs.length;i++){
            xs[i] = xs.length - i;
            System.out.print(xs[i] + " ");
        }
        System.out.println();

        // Sort the array in ascending order
        Arrays.sort(xs);
        // Output array
        System.out.println("\nSorted array: ");
        for(int i=0; i<xs.length;i++){
            System.out.print(xs[i] + " ");
        }
        System.out.println();


        // Sorting in any other order is more difficult.
        // One way is to copy our int array to an Integer array
        Integer[] is = new Integer[xs.length];
        for(int i=0; i<is.length; i++){
            is[i] = Integer.valueOf(xs[i]);
        }
        // Now sort in descending order
        Arrays.sort(is, Collections.reverseOrder());
        // Output array
        System.out.println("\nSorted array: ");
        for(int i=0; i<is.length;i++){
            System.out.print(is[i] + " ");
        }

    }
}