数组

组是引用数据类型

class Array{
    public static void main(String[] args){
            int[] array = {10,20,30,40,50};
                for(int index = 0,index<array.length,index++){
                    int i = array[index];
                 }
    }
   
}

二维数组

int[][] array=new int[]{{1,1,1},{2,2,2},{3,3,3}}

练习

image.png

第一题

public class Person {
    public static void main(String[] args){
        int[] a1 = new int[]{1,2,3,4};
        int[] a2 = new int[]{5,6,7,8,9,0};
        //方法一
        int[] x = a1;
        a1 = a2;
        a2 =x ;
        for (int v : a1){
            System.out.println(v);
        }
        for (int v : a2){
            System.out.println(v);
        }

        //方法二
        /*for(int i=0;i<a1.length;i++){
             int arr = a1[i];
             a1[i] = a2[i];
             a2[i]=arr;
        }
        for (int v : a1){
            System.out.print(v);
        }
        System.out.println("----------------");
        for (int v : a2){
            System.out.print(v);
        }*/
    }
}

第二题

public class Person {
    public static void main(String[] args){
       int[] array = new int[]{1,2,3,4,5,6,7,8};
       for (int i =0;i<array.length/2;i++){
           int x = array[i];
           array[i] = array[(array.length-1)-i];
           array[(array.length-1)-i] =x;

       }
        for (int v : array){
            System.out.print(v);
        }
    }
}

第四题

public class Person {
    public static void main(String[] args){
        int[] a = {1,2,3,4,5,6,7,8,9};
        int min = a[0];
        int max = 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.print(min);
            System.out.print(max);
        }
        System.out.println("最大："+max+"最小："+min);
    }
}

第五题

public class Person {
    public static void main(String[] args){
        int[] a = {1,2,3};
        int[] b = {4,5};
        int[] c = new int[b.length+a.length];
        for (int i = 0;i<a.length;i++){
            c[i]=a[i];
        }
        for (int i = 0;i<b.length;i++){
            c[a.length+i]=b[i];
        }
        for (int array:c){
            System.out.println(array);
        }
    }
}

第九题

public static void main(String[] args){
        int[] a = {1,4,7,3,5};
        for(int i=0 ;i<a.length;i++){
            for(int j = 0;j<a.length-1;j++){
                if(a[j]>a[j+1]){
                    int temp = a[j];
                    a[j]  = a[j+1];
                    a[j+1] = temp;
                }
            }

        }
        for(int v : a ){
            System.out.println(v);
        }
    }

第十题

分析：实现用户登入
1.先得注册用户名 密码 Scanner 
2.将用户名密码存入数组内 
3.登入时比较用户名和密码是否正确
10.
public static void main(String[] args){
        String[][] demo ={{"曾泽磊","123"},{"袁傻傻","111"},{"狗子","122"}};
        Scanner sc = new Scanner(System.in);
        System.out.println("请输入用户名");
        String user = sc.nextLine();
        System.out.println("请输入密码");
        String password = sc.nextLine();
        boolean b = false;
        for (int i =0; i<demo.length;i++){
            if (demo[0][0].equals(user)){
                if (demo[0][1].equals(password)){
                    System.out.println("登录成功");
                    b=true;
                }
                break;
            }
        }
        if (!b) {
            System.out.println("密码或账号错误");
        }
    }