Java 使用 if else 语句终止程序？
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Termination of program using if else statement?
提问by Quinn
trying to terminate program using negative numbers and if else statement . does anyone see whats wrong with this thanks.
尝试使用负数和 if else 语句终止程序。有没有人看到这有什么问题，谢谢。
import java.util.Scanner;
public class Assignment {
public static void main(String args[]){
int n;
int i=0;
System.out.print("Enter a Number:");
Scanner scanner = new Scanner(System.in);
n= scanner.nextInt();
int backUp = n;
if(n>0)
n=n/10;
i++;
else if(backUp = -1)
System.out.print("program terminated......");
System.exit(0);
System.out.println("Number of Digits in " +backUp +" is " +i);
}
}
回答by BobTheBuilder
First of all, =is for assigning values. Use ==for comparing.
首先，=用于赋值。使用==比较。
Also, you need to use {}after ifand elsestatements if you want to run more than one line.
此外，如果要运行多于一行，则需要使用{}afterif和else语句。
回答by Suresh Atta
else if(backUp = -1)
Should be
应该
else if(backUp == -1)
= assignment operator , ==is for comparing
= 赋值运算符， ==用于比较
And finally with missed {}
最后与错过 {}
if (n > 0) {
n = n / 10;
i++;
} else if (backUp == -1) {
System.out.print("program terminated......");
System.exit(0);
}else{
// do something else. I have no idea.
}
回答by Tobb
You are missing { }for your if-statements. In ifstatements without the { }, only the line following the if-statement will be affected by the outcome of the if-test.
这是因为丢失{ }了你的if-statements。在if没有 的语句中{ }，只有 if 语句后面的行会受到 的结果的影响if-test。
So:
所以：
if (condition)
doSomething();
doSomethingElse();
will execute doSomething()if condition == trueand doSomethingElse()no matter if condition == true.
将执行doSomething()ifcondition == true并且doSomethingElse()不管 if condition == true。
if (condition) {
doSomething();
doSomethingElse();
}
will execute both doSomething()and doSomethingElse(), if and only if condition == true.
将同时执行doSomething()and doSomethingElse()，当且仅当 condition == true 。
回答by Scott Pearson
You are using an assignment operator to evaluate a condition.
您正在使用赋值运算符来评估条件。
else if(backUp = -1)
should be
应该
else if(backup == -1)
回答by Rajendra arora
remove elseuse if(backup==-1).
删除else使用if(backup==-1).
回答by Alowaniak
First of all your indenting.
首先你的缩进。
Secondly, if you want to execute multiple statements given a certain condition you'll need to put it in a code block like if(x) { /* do multiple things */ }.
其次，如果你想在给定的条件下执行多条语句，你需要把它放在像if(x) { /* do multiple things */ }.
Thirdly, your else if(backUp = -1)is invalid because you need a boolean expression inside a if, backUp = -1is an assignment and thus does not evaluate to a boolean (you probably want backUp == -1).
第三，您else if(backUp = -1)的无效，因为您需要在 if 中使用布尔表达式，这backUp = -1是一个赋值，因此不会计算为布尔值（您可能想要 backUp == -1）。
And you probably want to loop the n = n/10; i++;part because now it will never count more than 1 digit.
而且您可能想要循环该n = n/10; i++;部分，因为现在它的计数永远不会超过 1 位数。
