java 如果添加的对象有重复，如何抛出异常
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how to throw an exception if the object that is being added has a duplicate
提问by Wahegurupal Singh
I have to add a new object to an array but throw an exception if that object already exists.I don't know what to add after 'throw___________;'. I have made the object class and also a class to hold an array of that object.I have also done the part where i have to add it to the array but i don't know what exception to throw if the object already exists in that array.
我必须向数组添加一个新对象，但如果该对象已存在，则抛出异常。我不知道在“throw_______;”之后要添加什么。我已经创建了对象类和一个类来保存该对象的数组。我还完成了必须将其添加到数组的部分，但我不知道如果该对象已存在于该数组中，我不知道要抛出什么异常大批。
回答by josivan
The straightforward to do is throw an existent exception. You can do something like.
最简单的方法是抛出一个存在的异常。你可以做类似的事情。
throw new IllegalArgumentException();
Or use the constructor with String parameter
或者使用带有 String 参数的构造函数
throw new IllegalArgumentException("The value is already in the list.");
You can see the documentation of IllegalArgumentExceptionon oracle website.
您可以在 oracle 网站上查看IllegalArgumentException的文档。
If you prefer to use a custom exception. You need to follow the suggestion of @3kings. But you have to user the newoperator. For example, throw new MyCustomeException().
如果您更喜欢使用自定义异常。您需要遵循@3kings 的建议。但是您必须使用new运营商。例如，throw new MyCustomeException()。
回答by Sriniketh
Create a custom exception classlike the one below:
创建一个自定义异常class，如下所示：
public class CustomException extends Exception
{
private static final long serialVersionUID = 1997753363232807009L;
public CustomException()
{
}
public CustomException(String message)
{
super(message);
}
public CustomException(Throwable cause)
{
super(cause);
}
public CustomException(String message, Throwable cause)
{
super(message, cause);
}
public CustomException(String message, Throwable cause,
boolean enableSuppression, boolean writableStackTrace)
{
super(message, cause, enableSuppression, writableStackTrace);
}
}
You can use it as follows:
您可以按如下方式使用它：
throw new CustomException("blah blah blah");
Refer this link: http://examples.javacodegeeks.com/java-basics/exceptions/java-custom-exception-example/
请参阅此链接：http: //examples.javacodegeeks.com/java-basics/exceptions/java-custom-exception-example/
回答by ifly6
Create a RuntimeExceptionby making a new class that extends RuntimeException. Or, you could just use a Setrather than an array. Thus, you would get automatic duplicate-checking.
通过创建一个RuntimeException扩展RuntimeException. 或者，您可以只使用 aSet而不是数组。因此，您将获得自动重复检查。
