数组练习

1.输入5个学生成绩，求和，求平均

package practise;

import java.util.Scanner;

public class B1 {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        // 输入5个学生成绩，求和，求平均
        Scanner input = new Scanner(System.in);
        double score[] = new double[5];
        double sum = 0;
        for (int i = 0; i < score.length; i++) {
            System.out.println("请输入第" + (i + 1) + "个学生的成绩");
            score[i] = input.nextDouble();
            sum += score[i];
        }
        System.out.println("学生成绩的和是" + sum);
        System.out.println("平均成绩是" + sum / 5);
    }

}

 

 2.给定数组{5,2,3,7,4,22,6}求最大最小

package practise;

public class B2 {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        // 给定数组{5,2,3,7,4,22,6}求最大最小
        int a[] = { 5, 2, 3, 7, 4, 22, 6 };
        int max = a[0], min = a[0];
        for (int i = 1; i < a.length; i++) {
            if (a[i] > max)
                max = a[i];
            if (a[i] < min)
                min = a[i];
        }
        System.out.println("最大值是" + max);
        System.out.println("最小值是" + min);
    }

}

 

3.输入5个学生成绩，求和，求最大最小

package practise;

import java.util.Scanner;

public class B3 {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        // 输入5个学生成绩，求和，求最大最小
        Scanner input = new Scanner(System.in);
        double score[] = new double[5];
        double sum = 0;
        for (int i = 0; i < score.length; i++) {
            System.out.println("请输入第" + (i + 1) + "个学生的成绩");
            score[i] = input.nextDouble();
            sum += score[i];
        }
        int max = (int) score[0], min = (int) score[0];
        for (int j = 0; j < score.length; j++) {
            if (score[j] > max)
                max = (int) score[j];
            if (score[j] < min)
                min = (int) score[j];
        }
        System.out.println("学生成绩的和是" + sum);
        System.out.println("学生成绩的最大值是" + max);
        System.out.println("学生成绩的最小值是" + min);
    }

}

 

 4.冒泡排序

package practise;

public class B4 {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        // 冒泡排序
        int[] a = { 4, 3, 6, 4, 2, 1, 7 };
        for (int i = 0; i < a.length - 1; i++) {
            for (int j = 0; j < a.length - 1 - i; j++) {
                if (a[j] > a[j + 1]) {
                    int temp = a[j];
                    a[j] = a[j + 1];
                    a[j + 1] = temp;
                }
            }
        }
        for (int i : a) {
            System.out.println(i);
        }
    }

}

 

 5.数组的查找

package practise;

import java.util.Scanner;

public class B5 {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        // 数组的查找
        int[] a = { 5, 3, 12, 7, 4 };
        System.out.println("输入要查找的数");
        Scanner input = new Scanner(System.in);
        int x = input.nextInt();
        int index = -1;
        for (int i = 0; i < a.length; i++) {
            if (x == a[i]) {
                index = i;
                break;
            }
        }
        if (index != -1) {
            System.out.println("找到了，下标是" + index);
        } else {
            System.out.println("没找到");
        }
    }

}