数组

4.1 什么是数组？

• 容器
  • 可以存多个同种类型的数据

4.2 Java中如何表示数组

• 定义数组
  • 数据类型[] 数组名;
  • 实例化数组

  • public class Main {
        public static void main(String[] args) {
    
            int[] arryList = new int[7];
            for (int i = 0 ;i<7;i++){
                arryList[i] =i*2;
                System.out.println(arryList[i]);
            }
    
    
        }
    }

  • 实例化数组
    • 静态赋值
    • 动态赋值

  • 数组名 = new 数据类型[长度]

  • 4.3

    

练习

//1.键盘录入5个数存入数组
public class One {
    public static void main(String[] args) {
        int[] arry =new int [5];
        System.out.println("请输入数据！");
        Scanner sc =new Scanner(System.in);
        for (int i=1;i<6;i++){//循环键入数据
            System.out.println("请第"+i+"次输入数据！");
            int a =sc.nextInt();
            arry[i-1]=a;//给数组赋值
        }
        for (int i = 0 ;i<5;i++){//循环赋值并取出
            System.out.println("第"+(i+1)+"次输入数据是"+arry[i]);
        }
    }
}

//取数
package arrylistTrain;
public class Two {
    public static void main(String[] args) {
        int[] arryList = new int[7];//定义数组
        for (int i = 0 ;i<7;i++){//循环赋值并取出
            arryList[i] =i*2;
            System.out.println(arryList[i]);
        }


    }

public class Three {
    public static void main(String[] args) {
        int[] arry =new int [5];
        System.out.println("请输入数据！");
        Scanner sc =new Scanner(System.in);
        for (int i=1;i<6;i++){//循环键入数据
            System.out.println("请第"+i+"次输入数据！");
            int a =sc.nextInt();
            arry[i-1]=a;//给数组赋值
        }
        int max=arry[0];
        for (int i=1;i<5;i++){
            if (max>=arry[i]){
                System.out.println("第"+(i)+"次比较max为"+max);
            }else {
                max=arry[i];
                System.out.println("第"+(i)+"次比较max为"+max);
            }
        }
    }
}

public class Four {
    public static void main(String[] args) {
        int[] arry =new int [5];
        System.out.println("请输入数据！");
        Scanner sc =new Scanner(System.in);
        for (int i=1;i<6;i++){//循环键入数据
            System.out.println("请第"+i+"次输入数据！");
            int a =sc.nextInt();
            arry[i-1]=a;//给数组赋值
        }
        int min=arry[0];
        for (int i=1;i<5;i++){
            if (min<=arry[i]){
                System.out.println("第"+(i)+"次比较min为"+min);
            }else {
                min=arry[i];
                System.out.println("第"+(i)+"次比较max为"+min);
            }
        }
    }
}

import java.util.Scanner;
//冒泡排序
public class Five {
    public static void main(String[] args) {
        int[] arry =new int [5];
        System.out.println("请输入数据！");
        Scanner sc =new Scanner(System.in);
        for (int i=1;i<6;i++){//循环键入数据
            System.out.println("请第"+i+"次输入数据！");
            int a =sc.nextInt();
            arry[i-1]=a;//给数组赋值
        }
        int n =arry.length;
        for (int i = 0;i<n;i++){//外层循环次数，等于数组长度
            for (int j = 0;j<5-(i+1);j++){//内层循环次数，每次冒泡确定一个最大数在数组末尾，每次内层循环比较次数少1
                int middle;//中间变量
                if (arry[j]>arry[j+1]){//冒泡交换顺序
                    middle=arry[j];
                    arry[j]=arry[j+1];
                    arry[j+1]=middle;
                }
            }
        }
        for (int i = 0 ;i<5;i++){//循环赋值并取出
            System.out.println(arry[i]);
        }
    }
}