程序流程控制

程序流程控制
顺序结构：程序从上到下逐行执行，中间无任何判断和跳转
分支结构：根据条件，选择性的执行某段代码
if–else和switch–case两种分支语句
循环结构：根据循环条件，重复性的执行某段代码
while
do–while
for三种循环语句
JDK1.5提供foreach循环，方便遍历集合，数组元素

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如何从键盘获取不同类型的变量，需要使用scanner类
具体实现步骤：
1 导包：import java.util.Scanner;
2 Scanner的实例化：Scanner scan=new Scanner(System.in);
3 调用Scanner类的相关方法 next()或者nextXxx()，来获取指定类型的变量：int score=scan.nextInt();

import java.util.Scanner;
public class text6{
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		System.out.println("请输入岳小鹏期末成绩: (0-100)");
		int score = scan.nextInt();
		if (score == 100) {
			System.out.println("BMW");
		} else if (score > 80 && score <= 99) {
			System.out.println("XS");
		} else if (score >= 60 && score <= 80) {
			System.out.println("ipad");
		} else {
			System.out.println("no");
		}
	}
}

嵌套

package text1;//num1,num2,num3从小到大输出
import java.util.Scanner;
public class text6{
	public static void main(String[] args) {
		Scanner scanner=new Scanner(System.in);
		int num1=scanner.nextInt();
		System.out.println("请输入第一个数字");
		int num2=scanner.nextInt();
		System.out.println("请输入第二个数字");
		int num3=scanner.nextInt();
		System.out.println("请输入第三个数字");
		if(num1>num2) {
			if(num3<num2) {
				System.out.println(num3+","+num2+","+num1);
			}else if(num3>num1) {
				System.out.println(num2+","+num1+","+num3);
			}else {
				System.out.println(num2+","+num3+","+num1);
			}
		}else {
			if(num3<num1) {
				System.out.println(num3+","+num1+","+num2);
				
			}else if(num3>num2){
				System.out.println(num1+","+num2+","+num3);
			}else {System.out.println(num1+","+num3+","+num2);
		}
	}
}
	}

如何在[a,b]获取一个随机数[10,99]
int value=(int)(Math.random( )90+10 );
公式：Math.random( )(b-a+1)+a

package text1;
import java.util.Scanner;
public class uu {
	public static void main(String[] args) {
		Scanner scanner=new Scanner(System.in);
		System.out.println("身高: (cm)");
		int height=scanner.nextInt();
		System.out.println("资产： （千万）");
		double wealth=scanner.nextDouble();
		//System.out.println("颜值：（false/true）");
		//boolean ishandsome=scanner.nextBoolean();
		System.out.println("颜值：（是/否）");
		String ishandsome=scanner.next();
		if(height>=180&&wealth>=1&&ishandsome.equals("是")) {
			System.out.println("ou");
		}else if(height>=180||wealth>=1||ishandsome.equals("是")) {
			System.out.println("ba");
		}else {
			System.out.println("gun");
			}
`

1 //switch–case

package text1;

import java.util.Scanner;

public class text8 {

	public static void main(String[] args) {
		Scanner scanner=new Scanner(System.in);
		System.out.println("A选项");
		System.out.println("B选项");
		System.out.println("C选项");
		System.out.println("D选项");
		System.out.println("请选择");
		String num=scanner.next();
		switch(num) {
		case "A":
			System.out.println("a");
			break;
		case "B":
			System.out.println("b");
			break;
		case "C":
			System.out.println("c");
			break;
		case "D":
			System.out.println("d");
			break;
		default:
			System.out.println("不确定");
		}
	

	}
	
}

String与int之间的强制类型转换

        int num1=100;
		String str="1000";
		System.out.println(str+11);
		int aa=Integer.valueOf(str);//String--->int强制类型转换
		System.out.println(aa+11);
		String str2=num1+"";//int--->String强制类型转换
	    System.out.println(str2+9);

2 //do–while先执行再判断

            int m=1000;
	    do {
	    	System.out.println("m="+m);
	    	m++;
	    }while(m<5);
	    System.out.println("------------------");//  syso+Alt+/+Enter

3 //foreach格式：for(数组的类型 变量名:数组名)目的：遍历数组

 int arr[]= {10,-20,30,40,-50};
	    for(int str1:arr) {
	    	System.out.println(str1);
	    }

4 //for循环

	    System.out.println("------------------");
	    for(int i=0;i<=5;i++) {
	    	System.out.println(i); 

5 //while

System.out.println("------------------");
	    int num3=0;
	    while(num3<5) {
	    	System.out.println(num3);
	    	num3++;

本文地址：https://blog.csdn.net/qq_50698099/article/details/111963821