java 为什么我会收到错误 unreachable 语句？
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/6966857/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Why do i get the error unreachable statement?
提问by Gen
Why do I get the error that line 92 is an unreachable statement? Basically what I'm trying to do is to skip some of the codes like 21-22-23... if the user inputs something like 11-12-13...
为什么我会收到第 92 行是一条无法访问的语句的错误消息？基本上我想做的是跳过一些像 21-22-23 这样的代码......如果用户输入像 11-12-13 这样的东西......
import java.util.*;
public class Words {
public static void main(String[] args) {
Scanner s = new Scanner(System.in);
System.out. print ("\n\tINTEGER TO WORDS") ;
System.out.print ("\n\nEnter a number between 1 and 9999: ") ;
int num = s.nextInt();
System.out. print ("\nThe answer is: ") ;
int tho = (num - (num % 1000)) ;
int h = (num - tho - (num % 100)) ;
int t = (num - tho - h - (num % 10)) ;
int o = (num - tho - h - t) ;
switch (tho)
{
case 9000:
System.out.print ("Nine Thousand ") ;
break ;
case 8000:
System.out.print ("Eight Thousand ") ;
break ;
case 7000:
System.out.print ("Seven Thousand ") ;
break ;
case 6000:
System.out.print ("Six Thousand ") ;
break ;
case 5000:
System.out.print ("Five Thousand ") ;
break ;
case 4000:
System.out.print ("Four Thousand ") ;
break ;
case 3000:
System.out.print ("Three Thousand ") ;
break ;
case 2000:
System.out.print ("Two Thousand ") ;
break ;
case 1000:
System.out.print ("One Thousand ") ;
break ;
}
switch (h)
{
case 100:
System.out.print ("One Hundred ") ;
break ;
case 200:
System.out.print ("Two Hundred ") ;
break ;
case 300:
System.out.print ("Three Hundred ") ;
break ;
case 400:
System.out.print ("Four Hundred ") ;
break ;
case 500:
System.out.print ("Five Hundred ") ;
break ;
case 600:
System.out.print ("Six Hundred ") ;
break ;
case 700:
System.out.print ("Seven Hundred ") ;
break ;
case 800:
System.out.print ("Eight Hundred ") ;
break ;
case 900:
System.out.print ("Nine Hundred ") ;
break ;
}
switch (t)
{
case 10:
System.out.print ("Ten ") ;
break ;
**switch (o)**
{
case 11:
System.out.print ("Eleven ") ;
break ;
case 12:
System.out.print ("Twelve ") ;
break ;
case 13:
System.out.print ("Thirteen ") ;
break ;
case 14:
System.out.print ("Fourteen ") ;
break ;
case 15:
System.out.print ("Fifteen ") ;
break ;
case 16:
System.out.print ("Sixteen ") ;
break ;
case 17:
System.out.print ("Seventeen ") ;
break ;
case 18:
System.out.print ("Eighteen ") ;
break ;
case 19:
System.out.print ("Nineteen ") ;
break ;
}
case 20:
System.out.print ("Twenty ") ;
break ;
case 30:
System.out.print ("Thirty") ;
break ;
case 40:
System.out.print ("Fourty ") ;
break ;
case 50 :
System.out.print ("Fifty ") ;
break ;
case 60:
System.out.print ("Sixty ") ;
break ;
case 70:
System.out.print ("Seventy ") ;
break ;
case 80:
System.out.print ("Eighty ") ;
break ;
case 90:
System.out.print ("Ninenty ") ;
break ;
}
switch (o)
{
case 1:
System.out.print ("One ") ;
break ;
case 2:
System.out.print ("Two ") ;
break ;
case 3:
System.out.print ("Three ") ;
break ;
case 4:
System.out.print ("Four ") ;
break ;
case 5:
System.out.print ("Five ");
break ;
case 6:
System.out.print ("Six ");
break ;
case 7:
System.out.print ("Seven ");
break ;
case 8:
System.out.print ("Eight ");
break ;
case 9:
System.out.print ("Nine ");
break ;
}
System.out. print ("\n") ;
}
}
回答by Jeremy
Because you breakright before it.
因为你break就在它之前。
回答by Mark Elliot
Because of the break;statement on line 88:
因为break;第 88 行的声明：
case 10:
System.out.print ("Ten ") ;
break ; // <-- problem is here
**switch (o)**
{
case 11:
System.out.print ("Eleven ") ;
You're telling the program "skip everything below this expression inside this switch statement until you're out of the switch statement", and the breakis unconditional, meaning it will alwaysoccur when inside case 10. The compiler is smart enough to recognize that this means, switch(o)can never execute, and so it alerts you that the "code cannot be reached".
你告诉程序“跳过这个 switch 语句中这个表达式下面的所有内容，直到你离开 switch 语句”，并且 thebreak是无条件的，这意味着它总是在 inside 时发生case 10。编译器足够聪明，可以识别出这意味着switch(o)永远无法执行，因此它会警告您“无法访问代码”。
回答by Hovercraft Full Of Eels
You've got code in a switch block after a break but without a preceding case, and that is unreachable code.
您在中断后的 switch 块中有代码但没有前面的情况，这是无法访问的代码。
But seriously, this code is borked and should be scrapped. I recommend you re-write this and use arrays to simplify, plan what you're going to write before you write it and only incrementally add small bits of code at a time, compiling after each bit of code is added and fixing any and all compilation errors before adding any new code.
但说真的，这段代码很无聊，应该报废。我建议您重新编写它并使用数组来简化，在编写之前计划您要编写的内容，并且一次只增量添加少量代码，在添加每一位代码后进行编译并修复任何和所有添加任何新代码之前的编译错误。
回答by subodh
Here is your little modified code and tested also.
这是您修改过的小代码并进行了测试。
import java.util.*;
导入 java.util.*;
public class Words {
公共课词{
public static void main(String[] args) {
Scanner s = new Scanner(System.in);
System.out. print ("\n\tINTEGER TO WORDS") ;
System.out.print ("\n\nEnter a number between 1 and 9999: ") ;
int num = s.nextInt();
System.out. print ("\nThe answer is: ") ;
int tho = (num - (num % 1000)) ;
int h = (num - tho - (num % 100)) ;
int t=0;
int o=0;
if(num>10 && num<20)
{
t=num;
}else{
t = (num - tho - h - (num % 10)) ;
o = (num - tho - h - t) ;
}
switch (tho)
{
case 9000:
System.out.print ("Nine Thousand ") ;
break ;
case 8000:
System.out.print ("Eight Thousand ") ;
break ;
case 7000:
System.out.print ("Seven Thousand ") ;
break ;
case 6000:
System.out.print ("Six Thousand ") ;
break ;
case 5000:
System.out.print ("Five Thousand ") ;
break ;
case 4000:
System.out.print ("Four Thousand ") ;
break ;
case 3000:
System.out.print ("Three Thousand ") ;
break ;
case 2000:
System.out.print ("Two Thousand ") ;
break ;
case 1000:
System.out.print ("One Thousand ") ;
break ;
}
switch (h)
{
case 100:
System.out.print ("One Hundred ") ;
break ;
case 200:
System.out.print ("Two Hundred ") ;
break ;
case 300:
System.out.print ("Three Hundred ") ;
break ;
case 400:
System.out.print ("Four Hundred ") ;
break ;
case 500:
System.out.print ("Five Hundred ") ;
break ;
case 600:
System.out.print ("Six Hundred ") ;
break ;
case 700:
System.out.print ("Seven Hundred ") ;
break ;
case 800:
System.out.print ("Eight Hundred ") ;
break ;
case 900:
System.out.print ("Nine Hundred ") ;
break ;
}
switch (t)
{
case 10:
System.out.print ("Ten ") ;
break ;
case 11:
System.out.print ("Eleven ") ;
break ;
case 12:
System.out.print ("Twelve ") ;
break ;
case 13:
System.out.print ("Thirteen ") ;
break ;
case 14:
System.out.print ("Fourteen ") ;
break ;
case 15:
System.out.print ("Fifteen ") ;
break ;
case 16:
System.out.print ("Sixteen ") ;
break ;
case 17:
System.out.print ("Seventeen ") ;
break ;
case 18:
System.out.print ("Eighteen ") ;
break ;
case 19:
System.out.print ("Nineteen ") ;
break ;
case 20:
System.out.print ("Twenty ") ;
break ;
case 30:
System.out.print ("Thirty") ;
break ;
case 40:
System.out.print ("Fourty ") ;
break ;
case 50 :
System.out.print ("Fifty ") ;
break ;
case 60:
System.out.print ("Sixty ") ;
break ;
case 70:
System.out.print ("Seventy ") ;
break ;
case 80:
System.out.print ("Eighty ") ;
break ;
case 90:
System.out.print ("Ninenty ") ;
break ;
}
switch (o)
{
case 1:
System.out.print ("One ") ;
break ;
case 2:
System.out.print ("Two ") ;
break ;
case 3:
System.out.print ("Three ") ;
break ;
case 4:
System.out.print ("Four ") ;
break ;
case 5:
System.out.print ("Five ");
break ;
case 6:
System.out.print ("Six ");
break ;
case 7:
System.out.print ("Seven ");
break ;
case 8:
System.out.print ("Eight ");
break ;
case 9:
System.out.print ("Nine ");
break ;
}
System.out. print ("\n") ;
}
}
}
