Java常见练习2

阶乘和

public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        System.out.println("请输入一个数：");
        int n=sc.nextInt();
        System.out.println("阶乘和为："+ret(n));

    }
    public static int ret(int n){
        int sum=0;
        int ret=1;
        //求阶乘
        int i,j;
        for(i=1;i<=n;i++){
            ret=1;
            for(j=1;j<=i;j++){
                ret*=j;
            }
            sum+=ret;
        }
        return sum;
    }

六合数

 public static void main(String[] args) {
    //六合数
        int num;
        for(num=0;num<999999;num++){
            int count=0;
            int tmp=num;
            while(tmp!=0) {
                count++;
                tmp=tmp/10;
            }//判断位数
            tmp=num;
            int j;
            int sum=0;
            for(j=0;j<count;j++){
                int ret;
                int a;
                int b=(int)Math.pow(10,j);
                a=(num/b)%10;
                ret=(int)Math.pow(a,6);
                sum+=ret;
            }
            if(num==sum){
                System.out.println(num);
            }

        }
}

最大值方法重载

 public static void main(String[] args) {
        int max=returnMAX(5,6);
        System.out.println("整数最大值为 "+max);
        double max2=returnMAX(5.89,101.534);
        System.out.println("小数最大值为 "+max2);
    }
    public static int returnMAX(int a,int b) {
    return (a>b)?a:b;
    }
    public static double returnMAX(double a,double b) {
        return (a>b)?a:b;
    }

递归-单独打印出每个数的每一位

public static void main(String[] args) {
everyOne(1235);
    }
    public static void everyOne(int a){
        if(a<10){
            System.out.println(a%10);;
            return ;
        }
        everyOne(a/10);
        System.out.println(a%10);

    }

递归-求任意一个数的每一位相加的值

 public static void main(String[] args) {
        sumEvery(1024);
    }
    public static int sumEvery(int n){
        int sum=0;
        if(n<10){
            return n;
        }
return n%10+sumEvery(n/10);
    }

递归-斐波那契数列

 public static void main(String[] args) {
        System.out.println(fib(6));
    }
    public static int fib(int n){
        if(n==1||n==2){
            return 1;
        }

        return fib(n-2)+fib(n-1);

    }

数组-元素均值+打印输出

public class array {
    public static void main(String[] args) {
    int []array1={1,2,3};
        System.out.println(Arrays.toString(array1));
        System.out.println(avg(array1));
    }
    public static int avg(int []array){
       int sum=0;

        for(int x:array){
          sum+=x;
        }

        return sum/array.length;
    }
}

数组-更改每个元素值

  public static void main(String[] args) {
int []array1={2,4,5,7};
transform(array1);
        System.out.println(Arrays.toString(array1));
    }
    public static void transform(int []array){
       int i=0;
        for(i=0;i<array.length;i++){
            array[i]=2*array[i];
        }
    }

数组-100个元素值分别为1...100

  public static void main(String[] args) {
        int N=100;
        int i=0;
        int []array=new int [N];
        for(i=0;i<array.length;i++){
            array[i]=i+1;
        }
        System.out.println(Arrays.toString(array));
    }

数组-冒泡排序

 public static void main(String[] args) {
int []array={15,57,2,34,68};
        System.out.println(Arrays.toString(array));
Bubble(array);
        System.out.println(Arrays.toString(array));
    }
    public static void Bubble(int []array){
        int i,j;
//i代表的是趟数
        for(i=0;i<array.length-1;i++){
            boolean flg=false;
            for(j=0;j<array.length-i-1;j++){
                if(array[j]>array[j+1]){
                    int tmp=array[j+1];array[j+1]=array[j];array[j]=tmp;
                    flg=true;
                }
            }
            if(!flg){
                break;
            }
        }
    }