What is the purpose of declaring exceptions? How do you declare an exception, and where? Can you declare multiple exceptions in a method header?

The purpose of declaring exceptions is to handle error conditions that may occur during the execution of a program. Exceptions can be used to signal that something unexpected has happened, such as an I/O error or an arithmetic overflow.

In Java, you declare an exception using the `throws` keyword in the method signature. For example:

public void readFile() throws IOException {
  // code that may throw an IOException
}

In this example, the `readFile()` method may throw an `IOException`, so it is declared in the method signature using the `throws` keyword.

You can declare multiple exceptions in a method header by separating them with commas. For example:

public void doSomething() throws IOException, SQLException {
  // code that may throw an IOException or a SQLException
}

By declaring the exceptions in the method signature, you are indicating to other developers that these exceptions may be thrown by the method and need to be handled appropriately.