value[slot] = data;

Checked Exceptions

Please keep in mind that Java bytecodes are executing, not the Java source code. However the bytecode file contains information about how lines of source code and bytecodes correspond. Line numbers are not given for bytecodes from the Java libraries.

Some exception types are checked exceptions, which means that a method must do something about them. The compiler checks to make sure that methods deal with these exceptions. There are two things a method can do with a checked exception:

1. Handle the exception in a catch{} block, or
2. throw the exception to the caller of the method.

For example, an IOException is a checked exception. Some programs use the readLine() method of BufferedReader for input. This method throws an IOException when there is a problem reading. Programs that use BufferedReader for input might to this.

public class DoesIO
{
  public static void main ( String[] a ) throws IOException
  {
    BufferedReader stdin = 
        new BufferedReader ( new InputStreamReader( System.in ) );

    String inData;
    inData = stdin.readLine();
    
    // More Java statements ...
  }
}

The reserved word throws says that this method does not catch the IOException, and that if one occurs in this method it will be thrown to the method that called this one. (In this example, it will be thrown back to the Java runtime system.)