Java练习之数组篇（Day1）

目录

1.一维数组初始化

2.二维数组初始化

3.二维数组的遍历

4.用一个数组存储学生的姓名，先输入人数，再输入每一个学员的姓名，最后遍历显示。

?5.统计学生分数的平均分、最高分、最低分和低于平均分的人数。

6.使用一个数组保存1-12月的英语单词，输入数字可以输出对应单词

7.随机产生10个1-100的偶数并按从小到大排序。

1.一维数组初始化

public class demo1 {
    public static void main(String[]args)
    {
        int [] arr=new int[5];
        String[] arr2={"aaa","eee","qqq"};
        double[] arr3=new double[]{2.3,66.4,7.54,6.33};
        for (int i = 0; i < arr2.length; i++) {
            System.out.println(arr2[i]);
        }
    }
}

2.二维数组初始化

public class demo2 {
    public static void main(String[]args)
    {
        int[][] arr=new int[][]{{1,2,3},{6,8,3},{66,44,3}};
        int[][] arr2={{4},{5,33},{8,94,11}};
        int[][] arr3=new int[3][2];
        for(int i=0;i< arr.length;i++)
        {
            for(int j=0;j<arr.length;j++)
            {
                System.out.print(arr[i][j]+" ");
            }
            System.out.println();
        }
    }
}

3.二维数组的遍历

public class demo3 {
    public static void main(String[] args) {
        int[][] arr = new int[][]{{55,94,4,7},{3,6,11,77},{43,65,85}};
        for (int i = 0; i < arr.length; i++) {
            for (int j = 0; j < arr[i].length; j++) {
                System.out.print(arr[i][j]+" ");
            }
            System.out.println();
        }
    }
}

4.用一个数组存储学生的姓名，先输入人数，再输入每一个学员的姓名，最后遍历显示。

public class demo5 {
    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        System.out.print("请输入学生人数：");
        int count=sc.nextInt();
        String[]arr=new String[count];
        for (int i = 0; i < arr.length; i++) {
            System.out.print("请输入第"+(i+1)+"个学生姓名:");
            arr[i]=sc.next();
        }
        System.out.println("所有学生姓名：");
        for(int i=0;i<arr.length;i++)
        {

            System.out.print(arr[i]+" ");
        }
    }
}

?5.统计学生分数的平均分、最高分、最低分和低于平均分的人数。

public class demo6 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("请输入人数：");
        int count = sc.nextInt();
        int[] grades = new int[count];
        String[] names = new String[count];
        for (int i = 0; i < grades.length; i++) {
            System.out.print("第" + (i+1) + "个学生姓名：");
            names[i] = sc.next();

            System.out.print("第" + (i+1) + "个学生成绩：");
            grades[i] = sc.nextInt();
        }
        sc.close();

        System.out.println("所有学员的成绩如下：");
        for (int i = 0; i < names.length; i++) {
            System.out.println(names[i] + ":" + grades[i]);
        }

        int max = grades[0];
        int min = grades[0];
        double sum = 0;
        for (int i = 1; i < grades.length; i++) {
            if(grades[i] > max){
                max = grades[i];
            }
            if(grades[i] < min){
                min = grades[i];
            }
            sum += grades[i];
        }
        double avg = sum/grades.length;

        System.out.println("最高分：" + max);
        System.out.println("最第分：" + min);
        System.out.println("平均分：" + avg);
        System.out.println("获得最高分：");
        for (int i = 0; i < names.length; i++) {
            if(max == grades[i]){
                System.out.println(names[i]);
            }
        }
        System.out.println("获得最第分的有：");
        for (int i = 0; i < names.length; i++) {
            if(min == grades[i]){
                System.out.println(names[i]);
            }
        }
        System.out.println("低于平均分的有：");
        int total = 0;
        for (int i = 0; i < names.length; i++) {
            if(grades[i] < avg){
                System.out.println(names[i]);
                total++;
            }
        }
        System.out.println("低于平均分的一共有：" + total +"人");
    }
}

6.使用一个数组保存1-12月的英语单词，输入数字可以输出对应单词

public class demo7 {
    public static void main(String[]args)
    {
        String[]month={"January","February","March","April","May","June","July","August","September","October","November","December"};
        Scanner sc=new Scanner(System.in);
        System.out.print("请输入1-12的数字：");
        int num=sc.nextInt();
        if(num>0&&num<13)
        {
            System.out.println("数字"+num+"所对应的月份是"+month[num-1]);
        }else{
            System.out.println("输入错误");
        }
    }
}

7.随机产生10个1-100的偶数并按从小到大排序。

public class demo8 {
    public static void main(String[] args) {
        int arr[]=new int[10];
        System.out.print("获取十个随机数并排序：");
        for (int i = 0; i < arr.length; i++) {
            arr[i]=(int)(Math.random()*50+1)*2;
        }
        for (int i = 1; i < arr.length; i++) {
            for (int j = 0; j < arr.length-1; j++) {
                if(arr[j]>arr[j+1])
                {
                    int temp=arr[j];
                    arr[j]=arr[j+1];
                    arr[j+1]=temp;
                }
            }
        }
        for (int i = 0; i < arr.length; i++) {
            System.out.print(arr[i]+" ");
        }
    }
}