An object's lock is a mechanism that is used by multiple threads to obtain synchronizedaccess to the object.A thread may execute a synchronized method of an object only after it has acquired theobject's lock. Allobjects and classes have locks. A class's lock is acquired on the class's Class object.

The Reader/Writer class hierarchy is character-oriented, and theInputStream/OutputStream class hierarchyis byte-oriented.

A class that is declared without any access modifiers is said to have package access. Thismeans that theclass can only be accessed by other classes and interfaces that are defined within thesame package.

The String literal "abc" is not a primitive value. It is a String object.

An event-listener interface defines the methods that must be implemented by an eventhandler for aparticular kind of event. An event adapter provides a default implementation of an eventlistenerinterface.

A component can handle its own events by implementing the required event-listenerinterface and addingitself as its own event listener.

The elements of a GridBagLayout are organized according to a grid. However, theelements are of differentsizes and may occupy more than one row or column of the grid. In addition, the rows andcolumns mayhave different sizes.

Java uses layout managers to lay out components in a consistent manner across allwindowing platforms.Since Java's layout managers aren't tied to absolute sizing and positioning, they are ableto accomodateplatform-specific differences among windowing systems.

A static variable is associated with the class as a whole rather than with specific instancesof a class. Nonstaticvariables take on unique values with each object instance.

The operating system's task scheduler allocates execution time to multiple tasks. Byquickly switchingbetween executing tasks, it creates the impression that tasks execute sequentially.

When a task's interrupt() method is executed, the task enters the ready state. The nexttime the task entersthe running state, an InterruptedException is thrown.

There are two types of casting, casting between primitive numeric types and castingbetween objectreferences. Casting between numeric types is used to convert larger values, such asdouble values, tosmaller values, such as byte values. Casting between object references is used to refer toan object by acompatible class, interface, or array type reference.

The JDK 1.02 event model uses an event inheritance or bubbling approach. In this model,components arerequired to handle their own events. If they do not handle a particular event, the event isinherited by (orbubbled up to) the component's container. The container then either handles the event orit is bubbled up toits container and so on, until the highest-level container has been tried.In the event-delegation...

The == operator compares two objects to determine if they are the same object inmemory. It is possible fortwo String objects to have the same value, but located indifferent areas of memory.

The enableEvents() method is used to enable an event for a particular object. Normally,an event is enabledwhen a listener is added to an object for a particular event. The enableEvents() method isused by objectsthat handle events by overriding their event-dispatch methods.

The File class encapsulates the files and directories of the local file system. TheRandomAccessFile classprovides the methods needed to directly access data contained in any part of a file.

If you are running Java on English Windows platforms, it is probably Cp1252. If you arerunning Java onEnglish Solaris platforms, it is most likely 8859_1..

Overridden methods must have the same name, argument list, and return type. Theoverriding method maynot limit the access of the method it overrides. The overriding method may not throwany exceptions thatmay not be thrown by the overridden method.

The exception propagates up to the next higher level try-catch statement (if any) orresults in the program'stermination.

Numeric promotion is the conversion of a smaller numeric type to a larger numeric type,so that integer andfloating-point operations may take place. In numerical promotion, byte, char, and shortvalues areconverted to int values. The int values are also converted to long values, if necessary.The long and floatvalues are converted to double values, as required.