Java 布尔值前的感叹号是什么？
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what does exclamation mark before the boolean?
提问by komal gupta
if(!checkSecondNum())
Where checkSecondNum is a method of boolean return type and why we used exclamatory sign in if statement please describe me in brief.
checkSecondNum 是一种布尔返回类型的方法，为什么我们在 if 语句中使用感叹号，请简要描述我。
回答by Suresh Atta
!called as boolean negation or Logical complimentand makes just inverts the result.
!称为布尔否定或逻辑恭维，并且只反转结果。
If your method checkSecondNum()returns falsethen
如果您的方法checkSecondNum()返回，false则
if(!checkSecondNum())
Becomes true.
成为true。
!falseequals to true
!false等于 true
回答by Aurand
You should take a look at the summary of Java operators:
你应该看看Java操作符的总结：
http://docs.oracle.com/javase/tutorial/java/nutsandbolts/opsummary.html
http://docs.oracle.com/javase/tutorial/java/nutsandbolts/opsummary.html
In this specific case, !is a logical NOT.
在这种特定情况下，!是一个合乎逻辑的NOT.
回答by Vallabh Patade
!is logical not operator.
That means when checkSecondNum()returns falseexecution will enter the if block.
!是逻辑非运算符。这意味着当checkSecondNum()返回false执行将进入 if 块。
!false = trueand
!true = false
!false = true和
!true = false
回答by Cobain
I think your progarm just wants to do the thing that when checkSecondNum()is not true, then executes the code in if{}. So your should use a !.
我认为你的程序只是想做这样的事情，whencheckSecondNum()不是真的，然后在if{}. 所以你应该使用一个!.
回答by kammy
- ! is Logical NOT operator.
- It will work reverse with your condition.
See simple example Given Below.
example-
n1=!true // it returns false
n2=!false // it returns true
n3=!"Cat" // it returns false - Hope you got meaning of NOT operator.Same in your case.
- ！是逻辑非运算符。
- 它会与您的情况相反。请参阅下面给出的简单示例。例子-
n1=!true // it returns false
n2=!false // it returns true
n3=!"Cat" // it returns false - 希望您理解 NOT 运算符的含义。在您的情况下也是如此。
