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freeCodeCamp/guide/chinese/java/instanceof-operator/index.md
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---
title: instanceof Operator
localeTitle: instanceof运算符
---
# `instanceof`运算符
`instanceof`运算符允许您检查`IS A`关系的有效性。如果在任何时候,我们不确定这一点,并且我们想在运行时验证这一点,我们可以执行以下操作:
```java
//assuming vehicle is an instance of Class `Car` the expression inside the 'if' will return true
if(vehicle instanceof Car){
//do something if vehicle is a Car
}
```
**注意** 如果将instanceof运算符应用于具有null值的任何变量则返回false。