Java

Question 1

Diagram of the exception hierarchy

Answer 1

Question 2

What are the 3 categories for exceptions and errors

Answer 2

CUE

• Checked Exceptions - Checked at compile time.
• Unchecked Exceptions - Usually programmer error. RuntimeException and subclasses.
• Errors - Not checked at compile time, but can be caught. E.g., AssertionError, ExceptionInInitializeError, OutOfMemoryError

Question 3

What is a required when you create a try block?

Answer 3

A try block must have at least one catch or finally block

Question 4

Describe the 4 different access modifiers

Answer 4

• public
• protected - subclass and package
• *default (package) - *package only
• private

Question 5

What are the two ways to create a thread?

Answer 5

Either by extending java.lang.Thread or by implementing java.lang.Runnable

Question 6

How do you create a thread using java.util.Thread

Answer 6

class Comet extends Thread {
    public void run( ) {
      System.out.println("Orbiting");
      orbit( );
    }
 }

Comet halley = new Comet( );

Question 7

How an example of implementing the Runnable interface

Answer 7

class Asteroid implements Runnable {
    public void run( ) {
      System.out.println("Orbiting");
      orbit( );
    }
 }

Asteroid maja = new Asteroid( );
 Thread majaThread = new Thread(maja);

Question 8

Name the 6 thread states

Answer 8

NEW - A thread that is created but not started

RUNNABLE - A thread that is available to run

BLOCKED - An “alive” thread that is blocked waiting for a monitor lock

WAITING - An “alive” thread that calls its own wait( ) or join( ) while waiting on another thread

TIMED_WAITING - An “alive” thread that is waiting on another thread for a specified period of time; sleeping

TERMINATED - A thread that has completed

Question 9

Describe thread priorities

Answer 9

The valid range of priority values is typically 1 through 10, with a default value of 5.

Lower priority threads yield to higher priority threads.