Cannot invoke "day_9.LOL.Weapon.setName(String)" because "weapon[0]" is null
时间: 2024-05-01 14:21:33 浏览: 7
这个错误发生的原因是你尝试在一个 null 对象上调用方法。在这个情况下,你尝试在一个空的 weapon 数组中的第一个元素上调用 setName 方法。你需要先创建一个 Weapon 对象并将其赋值给 weapon[0],然后才能调用 setName 方法。例如:
```
Weapon[] weapon = new Weapon[1];
weapon[0] = new Weapon();
weapon[0].setName("AK-47");
```
相关问题
Cannot invoke "String.equalsIgnoreCase(String)" because "code" is null
I apologize for the inconvenience. It seems that the variable "code" is currently null, which is causing the error when trying to invoke the `equalsIgnoreCase()` method on it.
To avoid this error, you should check if the "code" variable is null before invoking any methods on it. You can use an if statement or a null check to ensure that the variable has a value before performing any operations on it.
Here's an example of how you can modify your code to handle this situation:
```java
if (code != null && code.equalsIgnoreCase("yourString")) {
// Perform the desired operation
}
```
By checking if the "code" variable is null before invoking the `equalsIgnoreCase()` method, you can prevent the error from occurring.
Cannot invoke "java.net.URL.toExternalForm()" because "resource" is null
回答: 在给定的引用中,代码片段`URL location = null; location = (location == null) ? new URL("https://example.com") : location;`是为了避免在调用`toExternalForm()`方法时抛出空对象引用异常。这段代码使用了三元操作符来判断`location`是否为`null`,如果是,则将其赋值为一个新的URL对象。这样,在后续的代码中,就可以安全地使用`location`变量进行方法调用,比如`String locationString = location.toExternalForm();`。\[1\]
然而,根据您提供的问题信息`Cannot invoke "java.net.URL.toExternalForm()" because "resource" is null`,这个错误是由于`resource`变量为`null`导致无法调用`toExternalForm()`方法。请确保在调用`toExternalForm()`方法之前,`resource`变量已经被正确地初始化或赋值。如果`resource`是一个URL对象,可以使用类似的方法来避免空对象引用异常,比如使用三元操作符来判断并赋默认值。\[1\]\[3\]
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