问题描述
- 用 if ......else 语句 写的程序结果为什么会输出两次?以下是源代码:
- import java.util.Scanner;
public class Work0225_8 {
public static void main(String[] args) {
// 输入三个double型的数据,放入到abc三个变量中去
// 使用条件结构与交换逻辑将这三个变量中的值从小到大排列。
System.out.println(""请您输入第一个double型数据 :"");
Scanner mySc = new Scanner(System.in);
double a = mySc.nextDouble();
System.out.println(""请您输入第二个double型数据 :"");
double b = mySc.nextDouble();
System.out.println(""请您输入第三个double型数据 :"");
double c = mySc.nextDouble();
// a 最大的情况
if ((a > b) && (a > c)) {
if (b > c) {
a = a + c;
c = a - c;
a = a - c;
System.out.println(a + ""<"" + b + ""<"" + c);
} else if (b < c) {
a = a + c;
c = a - c;
a = a - c;
a = a + b;
b = a - b;
a = a - b;
System.out.println(a + ""<"" + b + ""<"" + c);
}
}
// b 最大的情况
if ((b > a) && (b > c)) {
if (a > c) {
b = b + c;
c = b - c;
b = b - c;
a = a + b;
b = a - b;
a = a - b;
System.out.println(a + ""<"" + b + ""<"" + c);
} else if (a < c) {
b = b + c;
c = b - c;
b = b - c;
System.out.println(a + ""<"" + b + ""<"" + c);
}
}
// c 最大的情况
if ((c > a) && (c > b)) {
if (a > b) {
a = a + b;
b = a - b;
a = a - b;
System.out.println(a + ""<"" + b + ""<"" + c);
} else if (a < b) {
System.out.println(a + ""<"" + b + ""<"" + c);
}
}
}
}
解决方案
if ((a > b) && (a > c))
这个分支会走到
然后a c被交换
if ((c > a) && (c > b)) 此时a=1 b=2 c=3,所以又满足
解决方案二:
要修改,你每个输出后加上一个return;就可以了。
解决方案三:
变量的值随着我们的运算过程会发生变化
解决方案四:
完全逻辑问题,你输1,2,3就一次了
你输3 ,2 ,1 在A最大里走一次,重新赋值后又在C最大里走一次
解决方案五:
加else if就1次了
if ((a > b) && (a > c)) {
if (b > c) {
a = a + c;
c = a - c;
a = a - c;
System.out.println(a + ""<"" + b + ""<"" + c);
} else if (b < c) {
a = a + c;
c = a - c;
a = a - c;
a = a + b;
b = a - b;
a = a - b;
System.out.println(a + ""<"" + b + ""<"" + c);
}
}
// b 最大的情况
else _if ((b > a) && (b > c)) {
if (a > c) {
b = b + c;
c = b - c;
b = b - c;
a = a + b;
b = a - b;
a = a - b;
System.out.println(a + ""<"" + b + ""<"" + c);
} else if (a < c) {
b = b + c;
c = b - c;
b = b - c;
System.out.println(a + ""<"" + b + ""<"" + c);
}
}
// c 最大的情况
_else if ((c > a) && (c > b)) {
if (a > b) {
a = a + b;
b = a - b;
a = a - b;
System.out.println(a + ""<"" + b + ""<"" + c);
} else if (a < b) {
System.out.println(a + ""<"" + b + ""<"" + c);
}
}
}
}
解决方案六:
那要怎样改才能变成输出一遍呢
解决方案七:
因为abc随着if判断会改变自身的值