package com.examplehub.basics;

import java.util.Arrays;

public class Array {

    public static void main(String[] args) {
        int[] numbers = {1, 2, 3, 4, 5};

        /*
         * numbers[0] = 1
         * numbers[1] = 2
         * numbers[2] = 3
         * numbers[3] = 4
         * numbers[4] = 5
         */
        System.out.println("numbers[0] = " + numbers[0]);
        System.out.println("numbers[1] = " + numbers[1]);
        System.out.println("numbers[2] = " + numbers[2]);
        System.out.println("numbers[3] = " + numbers[3]);
        System.out.println("numbers[4] = " + numbers[4]);

        /*
         * Array index is out of bounds
         */
        //System.out.println(numbers[-1]);
        //System.out.println(numbers[5]);


        /*
         * numbers[0] = 1
         * numbers[1] = 2
         * numbers[2] = 3
         * numbers[3] = 4
         * numbers[4] = 5
         */
        for (int i = 0; i < 5; i++) {
            System.out.println("numbers[" + i + "] = " + numbers[i]);
        }

        /*
         * Length of numbers = 5
         */
        System.out.println("length of numbers = " + numbers.length);

        /*
         * numbers[0] = 1
         * numbers[1] = 2
         * numbers[2] = 3
         * numbers[3] = 4
         * numbers[4] = 5
         */
        for (int i = 0; i < numbers.length; i++) {
            System.out.println("numbers[" + i + "] = " + numbers[i]);
        }

        /*
         * numbers[4] = 5
         * numbers[3] = 4
         * numbers[2] = 3
         * numbers[1] = 2
         * numbers[0] = 1
         */
        for (int i = numbers.length - 1; i >= 0; i--) {
            System.out.println("numbers[" + i + "] = " + numbers[i]);
        }

        /*
         * 12345
         */
        for (int number : numbers) {
            System.out.print(number);
        }
        System.out.println();

        /*
         * [1, 2, 3, 4, 5]
         */
        System.out.println(Arrays.toString(numbers));



        String[] company = {"Google", "Facebook", "Amazon", "Microsoft"};

        /*
         * company[0] = Google
         * company[1] = Facebook
         * company[2] = Amazon
         * company[3] = Microsoft
         */
        for (int i = 0; i < company.length; i++) {
            System.out.println("company[" + i + "] = " + company[i]);
        }

        /*
         * Google
         * Facebook
         * Amazon
         * Microsoft
         */
        for (String c : company) {
            System.out.println(c);
        }

        /*
         * [Google, Facebook, Amazon, Microsoft]
         */
        System.out.println(Arrays.toString(company));

        int[][] twoDimensionalNumbers = {
                {1, 2, 3},
                {4, 5, 6, 7},
                {8, 9},
                {10, 11, 12, 13, 14, 15}
        };

        /*
         * total rows  = 4
         */
        System.out.println("total rows  = " + twoDimensionalNumbers.length);

        /*
         * row 0 length = 3
         * row 1 length = 4
         * row 2 length = 2
         * row 3 length = 6
         */
        for (int i = 0; i < twoDimensionalNumbers.length; i++) {
            System.out.println("row " + i + " length = " + twoDimensionalNumbers[i].length);
        }

        /*
         * row 0 = 1 2 3
         * row 1 = 4 5 6 7
         * row 2 = 8 9
         * row 3 = 10 11 12 13 14 15
         */
        for (int i = 0; i < twoDimensionalNumbers.length; i++) {
            System.out.print("row " + i + " = ");
            for (int j = 0; j < twoDimensionalNumbers[i].length; j++) {
                System.out.print(twoDimensionalNumbers[i][j] + " ");
            }
            System.out.println();
        }

        /*
         * row 0 = [1, 2, 3]
         * row 1 = [4, 5, 6, 7]
         * row 2 = [8, 9]
         * row 3 = [10, 11, 12, 13, 14, 15]
         */
        for (int i = 0; i < twoDimensionalNumbers.length; i++) {
            System.out.println("row " + i + " = " + Arrays.toString(twoDimensionalNumbers[i]));
        }

        /*
         * 1 2 3
         * 4 5 6 7
         * 8 9
         * 10 11 12 13 14 15
         */
        for (int[] ints : twoDimensionalNumbers) {
            for (int num : ints) {
                System.out.print(num + " ");
            }
            System.out.println();
        }

        /*
         * [1, 2, 3]
         * [4, 5, 6, 7]
         * [8, 9]
         * [10, 11, 12, 13, 14, 15]
         */
        for (int[] ints : twoDimensionalNumbers) {
            System.out.println(Arrays.toString(ints));
        }


        int length = 5;
        int[] array = new int[length];
        for (int i = 0; i < 5; i++) {
            array[i] = i + 1;
        }

        /*
         * [1, 2, 3, 4, 5]
         */
        System.out.println(Arrays.toString(array));

    }
}

来源于examplehub/java

用于使用0以外的默认值进行初始化：

var arr = new int[1000];
Arrays.fill(arr, 1);

有多种方法可以在Java中声明数组：

float floatArray[]; // Initialize later
int[] integerArray = new int[10];
String[] array = new String[] {"a", "b"};

您可以在Sun教程网站和JavaDoc中找到更多信息。

我发现，如果您了解每个部分，这会很有帮助：

Type[] name = new Type[5];

类型[]是名为name的变量的类型（“name”称为标识符）。文字“Type”是基类型，括号表示这是该基的数组类型。数组类型又是它们自己的类型，这允许您创建像类型[][]（类型[]的数组类型）这样的多维数组。关键字new表示为新数组分配内存。括号之间的数字表示新阵列的大小以及要分配的内存。例如，如果Java知道基本类型type需要32个字节，并且您需要一个大小为5的数组，那么它需要在内部分配32*5=160个字节。

您还可以使用已经存在的值创建数组，例如

int[] name = {1, 2, 3, 4, 5};

这不仅创建了空白空间，而且用这些值填充了空白空间。Java可以判断基元是整数，并且有5个基元，因此可以隐式地确定数组的大小。

声明数组：int[]arr；

初始化数组：int[]arr=new int[10]；10表示数组中允许的元素数

声明多维数组：int[][]arr；

初始化多维数组：int[][]arr=new int[10][17]；10行17列和170个元素，因为10乘以17等于170。

初始化数组意味着指定数组的大小。

声明对象引用数组：

class Animal {}

class Horse extends Animal {
    public static void main(String[] args) {

        /*
         * Array of Animal can hold Animal and Horse (all subtypes of Animal allowed)
         */
        Animal[] a1 = new Animal[10];
        a1[0] = new Animal();
        a1[1] = new Horse();

        /*
         * Array of Animal can hold Animal and Horse and all subtype of Horse
         */
        Animal[] a2 = new Horse[10];
        a2[0] = new Animal();
        a2[1] = new Horse();

        /*
         * Array of Horse can hold only Horse and its subtype (if any) and not
           allowed supertype of Horse nor other subtype of Animal.
         */
        Horse[] h1 = new Horse[10];
        h1[0] = new Animal(); // Not allowed
        h1[1] = new Horse();

        /*
         * This can not be declared.
         */
        Horse[] h2 = new Animal[10]; // Not allowed
    }
}