21-多维数组

import java.util.Scanner;

public class OneYearOneArray {
    public static void main(String[] args) {
        // 声明六个变量， 分别代表六门科目的成绩
        int YuWenIndex = 0;
        int ShuXueIndex = 1;
        int WaiYuIndex = 2;
        int WuLiIndex = 3;
        int HuaXueIndex = 4;
        int ShengWuIndex = 5;

        // 每门课的名字
        String[] names = new String[6];
        names[YuWenIndex] = "语文";
        names[ShuXueIndex] = "数学";
        names[WaiYuIndex] = "外语";
        names[WuLiIndex] = "物理";
        names[HuaXueIndex] = "化学";
        names[ShengWuIndex] = "生物";

        // 每门课的成绩
        double[] year1 = new double[6];

        // 用随机数给成绩赋值
        for (int i = 0; i < 6; i++) {
            year1[i] = 80 + Math.random() * 20;
        }

        // 每门课的成绩
        double[] year2 = new double[6];

        // 用随机数给成绩赋值
        for (int i = 0; i < 6; i++) {
            year2[i] = 80 + Math.random() * 20;
        }

        // 每门课的成绩
        double[] year3 = new double[6];

        // 用随机数给成绩赋值
        for (int i = 0; i < 6; i++) {
            year3[i] = 80 + Math.random() * 20;
        }

        double[] yearToUse;

        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入要查看第几年的成绩：");
        int year = scanner.nextInt();

        switch (year) {
            case 1:
                yearToUse = year1;
                break;
            case 2:
                yearToUse = year2;
                break;
            case 3:
                yearToUse = year3;
                break;
            default:
                System.out.println("输入的年份不对，将查看的是最新一年的成绩");
                yearToUse = year3;
                break;

        }

        System.out.println("请输入要查看的成绩编号：");

        int scoreIndex = scanner.nextInt();

        System.out.println("第" + year + "年的" + names[scoreIndex] + "的成绩是：" + yearToUse[scoreIndex]);

    }
}

import java.util.Scanner;

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

        // 声明六个变量， 分别代表六门科目的成绩
        int YuWenIndex = 0;
        int ShuXueIndex = 1;
        int WaiYuIndex = 2;
        int WuLiIndex = 3;
        int HuaXueIndex = 4;
        int ShengWuIndex = 5;

        // 每门课的名字
        String[] names = new String[6];
        names[YuWenIndex] = "语文";
        names[ShuXueIndex] = "数学";
        names[WaiYuIndex] = "外语";
        names[WuLiIndex] = "物理";
        names[HuaXueIndex] = "化学";
        names[ShengWuIndex] = "生物";

        Scanner scanner = new Scanner(System.in);

        System.out.println("请输入共有多少年的成绩：");

        int yearCount = scanner.nextInt();

        double[][] scores = new double[yearCount][names.length];

        for (int i = 0; i < yearCount; i++) {
            for (int j = 0; j < names.length; j++) {
                scores[i][j] = 80 + Math.random() * 20;
            }
        }

        System.out.println("请问要查看第几年的成绩？");

        int yearToUse = scanner.nextInt() - 1; // 优化用户体验

        System.out.println("请问要查看第几科的成绩？");

        int scoreToUse = scanner.nextInt() - 1;

        System.out.println("第" + (yearToUse + 1) + "年的第" + (scoreToUse + 1) + "门的成绩是：" + scores[yearToUse][+scoreToUse]);

    }
}

public class OneArrayForAll {
    public static void main(String[] args) {
        // 声明六个变量， 分别代表六门科目的成绩
        int YuWenIndex = 0;
        int ShuXueIndex = 1;
        int WaiYuIndex = 2;
        int WuLiIndex = 3;
        int HuaXueIndex = 4;
        int ShengWuIndex = 5;

        // 每门课的名字
        String[] names = new String[6];
        names[YuWenIndex] = "语文";
        names[ShuXueIndex] = "数学";
        names[WaiYuIndex] = "外语";
        names[WuLiIndex] = "物理";
        names[HuaXueIndex] = "化学";
        names[ShengWuIndex] = "生物";

        int yearCount = 6;

        double[][] scores = new double[yearCount][names.length];

        for (int i = 0; i < yearCount; i++) {
            for (int j = 0; j < names.length; j++) {
                scores[i][j] = 80 + Math.random() * 20;
            }
        }
    }
}

/**
 * @ClassName: MultiDimensionArray
 * @Description: TODO
 * @Author: AI悦创
 * @Date: 2022/10/9 10:52
 * @Version: V1.0
 * @Blog: https://www.bornforthis.cn
 */
public class MultiDimensionArray {
    public static void main(String[] args) {
        // 创建一个double类型的二维数组
        double[][] multiDimensionArr = new double[3][5];

        // 循环查看每个数组元素的值，在给数组元素赋值前，数组元素的值其实都是每种类型的初始值。
        for (int i = 0; i < multiDimensionArr.length; i++) {
            for (int j = 0; j < multiDimensionArr[i].length; j++) {
                System.out.println("multiDimensionArr[" + i + "][" + j + "]=" + multiDimensionArr[i][j]);
            }
        }

        // 其实第一维的数组，每个元素都是一个下一维度的属于的变量。在这里我们可以改变这个变量的值
        // 也就是让它指向一个新的变量。
        multiDimensionArr[2] = new double[100];

        // 检查每个的数组的长度，发现最后一个的长度不一样了，因为它指向了新的数组。
        for (int i = 0; i < multiDimensionArr.length; i++) {
            System.out.println("multiDimensionArr[" + i + "].length=" + multiDimensionArr[i].length);
        }

    }
}

/Library/Java/JavaVirtualMachines/jdk-11.0.2.jdk/Contents/Home/bin/java -javaagent:/Applications/IntelliJ IDEA.app/Contents/lib/idea_rt.jar=60118:/Applications/IntelliJ IDEA.app/Contents/bin -Dfile.encoding=UTF-8 -classpath /Users/huangjiabao/GitHub/Java_Coder/Coder20/out/production/Coder20 MultiDimensionArray
multiDimensionArr[0][0]=0.0
multiDimensionArr[0][1]=0.0
multiDimensionArr[0][2]=0.0
multiDimensionArr[0][3]=0.0
multiDimensionArr[0][4]=0.0
multiDimensionArr[1][0]=0.0
multiDimensionArr[1][1]=0.0
multiDimensionArr[1][2]=0.0
multiDimensionArr[1][3]=0.0
multiDimensionArr[1][4]=0.0
multiDimensionArr[2][0]=0.0
multiDimensionArr[2][1]=0.0
multiDimensionArr[2][2]=0.0
multiDimensionArr[2][3]=0.0
multiDimensionArr[2][4]=0.0
multiDimensionArr[0].length=5
multiDimensionArr[1].length=5
multiDimensionArr[2].length=100

Process finished with exit code 0