java词汇(编辑修改稿)

java词汇(编辑修改稿)内容摘要：

ctor. The JVM calls the finalizer for you as appropriate。 you never call a finalizer directly. Think of the finalizer as a friendly warning from the virtual machine. Your finalizer should perform two tasks: performing whatever cleanup is appropriate to the object, and calling the superclass finalizer. If you do not have any cleanup to perform for an object, then you‟re better off not adding a finalizer to the class. Floatingpoint literals Floatingpoint literals are defined as double by default, but if you want to specify in your code a number as float, you may attach the suffix F to the number. Floatingpoint numbers Floatingpoint numbers are defined as a number, a decimal symbol, and more numbers representing the fraction. FlowLayout manager This layout manager arranges ponents within the container from left to right. When the container runs out of room on the current row FlowLayout resumes positioning ponents on the next row. FocusEvent A ponent generates a FocusEvent when it gains or loses keyboard focus. The event ID is set to either FOCUS_GAINED or focus lost. There are two types of focus events, permanent and temporary. Permanent focus events indicate that another ponent has gained the focus, whereas temporary focus events indicate that the ponent has lost focus temporarily due to window deactivation or scrolling. For loop A flow control statement is used when a program needs to iterate a section of code a known number of times. There are three main parts to a for statement. They are the declaration and initialization of variables, the expression, and the incrementing or modification of variables. Each of the sections are separated by semicolons. The for loop is a remarkable tool for developers because it allows you to declare and initialize zero, one, or multiple variables inside the parenthesis after the for keyword. Garbage collection The process by which memory requested, but no longer in use, by a Java application is reclaimed by the Java VM. Generational garbage collectors Generational garbage collectors make the tradeoff of running faster with the cost of leaving garbage lying around longer. With today‟s large 词汇表█ 7 memory machines, this is a very reasonable tradeoff to make. GridBagLayout layout manager The GridBagLayout layout manager allows the placement of ponents that are aligned vertically and/or horizontally without constraining those ponents to be a particular size, height, or width. The GridBagLayout acplishes this by defining a dynamic grid of cells. The constraints object passed when the ponent is added to the container determine how many cells the ponent enpasses. GridLayout manager This layout manager arranges ponents in a grid within a container. Each cell in the grid is of equal dimensions. The GridLayout manager ignores the preferred size of each ponent and resizes them to exactly fit each cell‟s dimensions. As each ponent is added to the container the GridLayout inserts them across each column until that row is filled and then starts at the first column of the next row. Guarded region A section of code that is watched for errors to be handled by a particular group of handlers. HashMap class The HashMap class is roughly equivalent to Hashtable, except that it is not synchronized for threads and it permits null values to be stored. Heap Java manages memory in a structure called a heap. Every object that Java creates is allocated in the heap, which is created at the beginning of the application and managed automatically by Java. Hexadecimal literals Hexadecimal numbers are constructed using 16 distinct symbols. The symbols used are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, and F. Identifiers Identifiers are names that we assign to classes, methods, and variables. Java is a casesensitive language, which means identifiers must have consistent capitalization throughout. Identifiers can have letters and numbers, but a number may not begin the identifier name. Most symbols are not allowed, but the dollar sign ($) and underscore (_) symbols are valid. See also Reference variable. If statement If statements test an expression for a Boolean result. This is achieved by using one or more of Java‟s relational operators inside the parenthesis of the statement to pare two or more variables. Also, you can simply use the reserved word true as the expression to force execution of the block of code. See also Decision statement. Import statement Import statements allow us to refer to classes without having to use a fully qualified name for each class. Import statements do not make classes accessible。 all classes in the classpath are accessible. Inheritance Inheritance is an objectoriented concept that provides for the reuse and modification of an existing type in such a way that many types can be manipulated as a single type. In Java, inheritance is achieved with the extends keyword. Inner classes Inner classes are a type of class and follow most of the same rules as a 8 █ Sun认证 Java 2程序员学习指南 (Exam 310025) 第二版（影印本） normal class. The main difference is an inner class is declared within the curly braces of a class or even within a method. Inner classes are also classes defined at a scope smaller than a package. See also Anonymous inner classes。 Local inner classes。 Member inner classes。 Static inner classes. InputEvent class An InputEvent is an abstract class that serves as the base class for MouseEvent and KeyEvent. InputEvent defines the following method to determine the time of the event. Instance Once the class is instantiated, it bees an object. A single object is referred to as an “instance” of the class from which it was instantiated. Instance initializer An instance initializer (an alternative to lazy initialization) is a block of code (not a method!) that automatically runs every time you create a new i。