Code

代码

输出

public class One{
	public static void main(String[] args){
		System.out.println("hello world");
	}
}

键盘输入

import java.util.Scanner;
public class Two{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		System.out.println("Please input data = ");
		double x = sc.nextDouble();
		System.out.println("Please input character = ");
		string y = sc.next();
		System.out.println(y + x);
    }
}

if

import java.util.Scanner;
public class Three{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		System.out.println("Please input mouth = ");
		int mouth = sc.nextInt();
		if(mouth >= 3 && mouth <= 5){
			System.out.println("Spring");
		}else if(mouth >= 6 && mouth <= 8){
		            System.out.println("Summer");
		}else if(mouth >= 9 && mouth <= 11){
			System.out.println("Autumn");
		}else if(mouth == 12 || mouth ==1 || mouth == 2){
			System.out.println("Winter");
		}else{
			System.out.println("Error");
		}
	}
}

switch

import java.util.Scanner;
public class Four{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		System.out.println("Please input mouth = ");
		int mouth = sc.nextInt();
		switch(mouth){
			case 3:
			case 4:
			case 5:
				System.out.println("Spring");
				break;
			case 6:
			case 7:
			case 8:
				System.out.println("Summer");
			    break;
			case 9:
			case 10:
			case 11:
				System.out.println("Autumn");
				break;
			case 12:
			case 1:
			case 2:
				System.out.println("Winter");
				break;
			default:
				System.out.println("Error");
				break;
		}
	}
}

比较大小

import java.util.Scanner;
public class Five{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		System.out.println("Piease input x = ");
		double x = sc.nextDouble();
		System.out.println("Please input y = ");
		double y = sc.nextDouble();
		System.out.println("Please input z = ");
		double z = sc.nextDouble();
	
		if(x > y){
			if(x > z)
	 			System.out.println("max = " + x);
			else
				System.out.println("max = " + z);
		}else{
	    	if(y > z)
				System.out.println("max = " + y);
	        else
	            System.out.println("max = " + z);
	    }
	}
}

for

import java.util.Scanner;
public class Six{
	public static void main(String[] args) {
		int sum = 0;
		for(int i = 1; i <= 100; i++){
			if(i % 2 == 1){
		    	sum += i;
		    }
		}
		System.out.println(sum);
	}
}

计数器

import java.util.Scanner;
public class Seven{
	public static void main(String[] args) {
		int count = 0;
        for(int i = 100; i <= 999; i++){
            int a = i % 10;
            int b = i / 10 % 10;
            int c = i / 100;
            if(a * a * a + b * b * b + c * c * c == i){
                System.out.println(i);
                count++;
            }
        }
        System.out.println(count);
	}
} 

while

import java.util.Scanner;
public class Eight{
	public static void main(String[] args) {
		int count = 0;
        int i = 100;
        while(i <= 999){
            int a = i % 10;
            int b = i / 10 % 10;
            int c = i / 10 / 10 % 10;
            if (a * a * a + b * b * b + c * c* c == i){
                System.out.println(i);
                count++;
            }
            i++;
        }
        System.out.println(count);
    }
}

do while

import java.util.Scanner;
public class Nine{
	public static void main(String[] args) {
        int count = 0;
        int i = 100;
        do{
            int a = i % 10;
            int b = i / 10 % 10;
            int c = i / 10 / 10 % 10;
            if (a * a * a + b * b * b + c * c* c == i) {
                System.out.println(i);
                count++;
            }
            i++;
        }
        while(i <= 999);
        System.out.println(count);
    }
}

无限循环

import java.util.Scanner;
public class Ten{
	public static void main(String[] args) {
		while(ture){
			System.out.println("Over");
		}
	}
}
import java.util.Scanner;
public class Ten{
	public static void main(String[] args) {
		if(;;){
			System.out.println("over");
		}
	}
}

for嵌套

import java.util.Scanner;
public class Eleven{
	public static void main(String[] args) {
        for(int i = 1; i <= 9; i++){
            for(int j = 1; j <= i; j++){
                int k = i * j;
                System.out.print(i + "*" + j + "=" + k + '\t');
            }
            System.out.println();
        }
    }
}

重载方法

public class Twelve {
    public static void main(String[] args){
        boolean x = isEquals(20,30);
        System.out.println(x);
    }

    public static boolean isEquals(int a, int b){
        return a == b;
    }

    public static boolean isEquals(double a, double b){
        return a == b;
    }
}

一维数组遍历

public class Thirteen{
	public static void main(String[] args){
        int[] arr1 = new int[5];
        arr1[0] = 1;
        arr1[1] = 2;
        arr1[2] = 3;
        arr1[3] = 4;
        arr1[4] = 5;
        print(arr1);

        System.out.println("---------");

        int[] arr2 = {11,22,33,44,55};
        print(arr2);
    }

    public static void print(int[] arr){
        for(int i = 0; i < arr.length; i++){
            System.out.println(arr[i]);
        }
    }
}

二维数据遍历

public class Fourteen{
    public static void main(String[] args){
        int[][] arr1 = new int[3][2];
        arr1[0][0] = 1;
        arr1[0][1] = 2;
        arr1[1][0] = 3;
        arr1[1][1] = 4;
        arr1[2][0] = 5;
        arr1[2][1] = 6;

        int[][] arr2 = {{1,2,3},{4,5},{6,7,8,9}};
        print(arr1);
        System.out.println("---------");
        print(arr2);
    }
    public static void print(int[][] arr){
        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();
        }
    }
}

整数反转

import java.util.Scanner;
public class Solution1 {
    public static void main(String[] args){
        long boundary1 = (long)Math.pow(2, 31);	//改变溢出值在此更改boundary1
        long boundary2 = boundary1 - 1;
        Scanner sc = new Scanner(System.in);
        System.out.println("Please input digit(" + -boundary1 + "~" + boundary2 + ") = ");
        long digit = sc.nextLong();
        int digits = 1;
        for(int i = 0; i < 10; i++){	//改变溢出值位数在此更改i
            long divisor = (long)Math.pow(10, i);
            if(digit > -10 * divisor && digit < 10 * divisor){
                break;
            } else{
                digits++;
            }
        }
        if(digit > -boundary1 && digit < boundary2) {
            long rvDigit = reverse(digit, digits);
            if(rvDigit > -boundary1 && rvDigit < boundary2){
                System.out.println(rvDigit);
            }else{
                System.out.println("0");
            }
        }else{
            System.out.println("Illegal character");
        }
    }
    public static long reverse(long x, int y){
        long arr1[] = new long[y];
        for(int i = 0; i < y; i++){
            long divisor = (long)Math.pow(10, i);
            arr1[i] = x / divisor % 10;
        }
        reverseArr(arr1);
        long z = 0;
        for(int i = 0; i < y; i++){
            long divisor = (long)Math.pow(10, i);
            z += arr1[i] * divisor;
        }
        return z;
    }
    public static void reverseArr(long arr[]){
        for(int i = 0; i < arr.length / 2; i++){
            long temp = arr[i];
            arr[i] = arr[arr.length - 1 - i];
            arr[arr.length - 1 - i] = temp;
        }
    }
}

private封装

public class Fifteen {
    public static void main(String[] args){
        Person p =new Person();
        p.setName("张三");
        p.getName();
        p.setAge(20);
        p.getAge();
        p.setMale(false);
        p.getMale();
        p.speak();
    }
}

class Person {
    private String name;
    private int age;
    private boolean male;

    public void speak(){
        if(age != 0) {
            if (male == true) {
                System.out.println("Name is " + name + "; Age is " + age + "; Man");
            } else {
                System.out.println("Name is " + name + "; Age is " + age + "; Woman");
            }
        }else{
            System.out.println("No answer");
        }
    }

    public void setAge(int age){
            if(age > 0 && age < 121){
                this.age = age;
            }else{
                System.out.println("Illegal character");
            }
    }
    public int getAge(){
        return age;
    }

    public void setName(String name){
        this.name = name;
    }
    public String getName(){
        return name;
    }

    public void setMale(boolean male){
        this.male = male;
    }
    public boolean getMale(){
        return male;
    }
}

本文地址：https://blog.csdn.net/weixin_54231215/article/details/112168325