Arrays

import java.util.Arrays;

public class Felder {
    public static void main(String[] args) {
        int[] zahlen = {5, 3, 9, 1, 7};             // direkt mit Werten
        String[] namen = new String[3];             // 3 Plätze, anfangs null
        double[] preise = new double[4];            // anfangs 0.0
        namen[0] = "Mia";

        System.out.println(zahlen[0] + " " + zahlen[zahlen.length - 1] + " " + zahlen.length);
        System.out.println(Arrays.toString(namen) + " " + Arrays.toString(preise));
        zahlen[1] = 30;
        System.out.println(Arrays.toString(zahlen));
        try {
            System.out.println(zahlen[5]);
        } catch (ArrayIndexOutOfBoundsException e) {
            System.out.println("Fehler: " + e.getMessage());
        }
    }
}

import java.util.Arrays;

public class Werkzeuge {
    public static void main(String[] args) {
        int[] z = {5, 3, 9, 1, 7};
        int[] kopie = Arrays.copyOf(z, z.length);
        Arrays.sort(z);
        System.out.println(Arrays.toString(z) + " " + Arrays.toString(kopie));
        System.out.println(Arrays.binarySearch(z, 7) + " " + Arrays.equals(z, kopie));
        System.out.println(Arrays.stream(z).sum() + " " + Arrays.stream(z).max().getAsInt() + " " + Arrays.stream(z).average().getAsDouble());
        int[] b = new int[5];
        Arrays.fill(b, 7);
        System.out.println(Arrays.toString(b) + " " + Arrays.toString(Arrays.copyOfRange(z, 1, 3)));
    }
}

import java.util.Arrays;

public class Verweis {
    public static void main(String[] args) {
        int[] a = {1, 2, 3};
        int[] b = a;
        int[] c = a.clone();
        b[0] = 99;
        System.out.println(Arrays.toString(a) + " " + Arrays.toString(c));
        System.out.println(a == b);
        System.out.println(a.equals(c) + " " + Arrays.equals(a, c));
    }
}

import java.util.Arrays;

public class Matrix {
    public static void main(String[] args) {
        int[][] m = {
            {1, 2, 3},
            {4, 5, 6}
        };
        System.out.println(m[1][2] + " " + m.length + " " + m[0].length);
        for (int[] zeile : m) System.out.println(Arrays.toString(zeile));

        int[][] t = new int[3][2];                    // Transponieren
        for (int i = 0; i < m.length; i++)
            for (int j = 0; j < m[i].length; j++)
                t[j][i] = m[i][j];
        System.out.println(Arrays.deepToString(t));
    }
}

import java.util.*;

public class Eigene {
    public static void main(String[] args) {
        String[] woerter = {"Banane", "Kiwi", "Apfel", "Zitrone"};
        Arrays.sort(woerter);
        System.out.println(Arrays.toString(woerter));
        Arrays.sort(woerter, Comparator.comparing(String::length).thenComparing(Comparator.naturalOrder()));
        System.out.println(Arrays.toString(woerter));
        Arrays.sort(woerter, Collections.reverseOrder());
        System.out.println(Arrays.toString(woerter));
    }
}