whlie和if...else 和 switch()case()break
if...else
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package com.scanner;
import java.util.Scanner;
//if判断
public class Demo01 {
public static void main(String[] args) {
int i = 0;
float f = 0.0f;
System.out.println("请输入整数:");
Scanner A = new Scanner(System.in);
if (A.hasNextInt()) {
i = A.nextInt();
System.out.println("整数为:" + i);
} else {
A.next();
System.out.println("输入不是整数");
}
System.out.println("请输入小数:");
if (A.hasNextFloat()) {
f = A.nextFloat();
System.out.println("小数为:" + f);
} else {
System.out.println("输入不是小数");
}
A.close();
}
}
while
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package com.scanner;
import java.util.Scanner;
//whlie
// 输入数字,非数字结束,求和,平均数
public class Demo03 {
public static void main(String[] args) {
double sum = 0;
int x = 0;
System.out.println("请输入数据,非数字结束");
Scanner scanner = new Scanner(System.in);
while (scanner.hasNextDouble()) {
//当while()为ture,{}会一直循环
double y = scanner.nextDouble();
sum = sum + y;
x = x + 1;
System.out.println("和为:" + sum + " ,共" + x + "数");
}
System.out.println("和为:" + sum);
System.out.println("平均为:" + (sum / x));
//do()while()至少走一次
int i = 0;
int Sum = 0;
do {
Sum = Sum + i;
i++;
}
while (i <= 100);
System.out.println(Sum);
}
}
switche()case()break
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//switch case break
public class SwitchCsaeBreak {
public static void main(String[] args) {
String name="小哥";
//JDK7的新特性,表达式结果可以是字符串! ! !
// 字符的本质还是数字
//反编译java---class (字节码文件)----反编译(IDEA)
switch (name){
case"小姐姐":
System.out.println("小姐姐");
break;
case "小哥":
System.out.println("小哥哥");
break;
default:
System.out.println("弄啥呦!");
}
}