Java Basic Syntax Summary 1

I. Identifiers and Character sets

The Java language specifies that identifiers begin with a letter, an underscore "_" or a dollar sign "$", followed by a sequence of characters that can be followed by a number, letter, underscore, or dollar sign. Java identifiers are case-sensitive, have no length limit, and can be given an arbitrary length name for an identifier, but the keyword cannot be used as an identifier. To enhance the readability of the program, Java makes the following conventions:

1. Classes, interfaces: Nouns are usually used, and the first letter of each word is capitalized

2. Method: Usually use verbs, lowercase letters, and then separate each word with uppercase letters

3. Constants: All uppercase, the words are separated by underscores

4. Variables: Usually use nouns, lowercase letters, followed by uppercase letters to separate each word, avoid using the $ symbol.

The Java language uses the international character set (Unicode). The Unicode character set defines a set of international standard character sets. The usual ASCII code is 8 bits, while each character in the Unicode character set occupies 16 bits, or 2 bytes, and the entire character set consists of 65,336 characters, compatible with ASCII, and the 256 characters that precede the Unicode character set are ASCII codes. In addition to representing 256 ASCII codes, Unicode can also represent Chinese characters, Latin, Greek letters, Korean, and so on.

Summary of Java Identifiers: 1. Consist of letters, numbers, _ or $, which cannot begin with a number; 2. Strictly case-sensitive; 3. Unlimited length

Second, the key word

A list of common Java keywords is as follows:

Key words	Meaning
Abstract	It is used in the declaration of a class to indicate that a class cannot be instantiated, but can be inherited by other classes. An abstract class can use abstract methods, and abstract methods do not need to be implemented, but they need to be implemented in subclasses
Boolean	Boolean type, only true or false
Break	Stop, and jump out of this layer loop
Byte	8bit (bit), that is, 8 x 1/0 means, binary
Case	Used to define a set of branch selections, and if a value is the same as the value given in a switch, it is executed from that branch.
Catch	Used to declare a block that runs when a run-time error or a non-runtime exception occurs in a try statement block.
Char	Used to define a character type
Class	Class
Const	In Java, the const is used as a reserved word for expansion, with the same reserved word for expansion and Goto. You can use the final keyword. Final can also be used to declare a method or class that cannot be inherited by a method or class that is declared final. General c is const corresponding to Java with final
Continue	Used to interrupt the current loop process, starting at the end of the current loop, and if followed by a label, start execution from the label's corresponding location.
Default	In conjunction with switch and case, the output or the statement following the default is not found when a match is located.
Do	Used to declare a loop in which the end condition of the loop can be set by the while keyword
Double	Used to define a variable of type double
Else	If the condition of the IF statement is not satisfied, the statement executes.
Extends	extends inherits class X by Extend class Y to add functionality, or adding a variable, or adding a method, or overriding a method of Class Y. An interface extends another interface to add a method.
False	It's fake.
Final	A keyword for a Java language. You can define only one entity at a time, and you cannot change it or inherit it later. More strictly speaking: A final modified class cannot be quilt-like, a final modified method cannot be overridden, and a final modified variable cannot change its initial value.
Finally	Used to execute a piece of code regardless of whether there are exceptions or run-time errors in the Try statement defined earlier.
Float	Used to define a floating-point variable
For	Used to declare a loop. Programmers can specify the statements to loop, introduce conditions and initialize variables.
Goto	Java does not provide a goto statement, although it is a Java keyword, but only used in the C language
If	A keyword in the Java programming language that is used to generate a conditional test, and if the condition is true, execute the IF statement.
Implements	A keyword in the Java (TM) programming language, which is optional in the declaration of the class, to indicate the interface that the current class implements.
Import	A keyword in the Java (TM) programming language that indicates a class or entire package to be referenced at the beginning of the source file, so that you do not have to add the package name when you use it.
Instaceof	A two-operand Java (TM) language keyword that is used to test whether the run-time type of the first parameter is compatible with the second parameter.
Int	A keyword in Java (TM) used to define an shaping variable
Interface	A keyword in Java (TM) used to define a series of methods and constants. It can be implemented by class by implements keywords.
Long	Used to define a long type of variable
Native	Local methods.
New	Used to create a new method
Null	When the string type is not assigned a value, the value of the variable is null
Package	The meaning of the package
Private	Used in the sound of a method or variable. It means that the method or variable can only be accessed by other elements of the class.
Protected	Used in declarations of methods and variables, which indicates that the method or variable can only be accessed by elements in the same class, in subclasses, or in classes within the same package.
Public	Used in declarations of methods and variables, which means that the method or variable can be accessed by elements in other classes.
Return	Used to end the execution of a method. It can be followed by a value that is required in a method declaration.
Short	Used to define a variable of type short.
Static	Used to define a variable as a class variable. class maintains only a copy of a class variable, regardless of how many instances of the class are currently present. "Static" can also be used to define a method as a class method. A class method is called by a class name instead of a specific instance, and only class variables can be manipulated.
Super	Parent class
Switch	is a SELECT statement to use with Case,default,break.
Synchronized	Thread synchronization
This	An instance of the class used to represent the occurrence of it. This can be used to access class variables and class methods.
Threadsafe
Throw	Allows the user to throw an exception object or any object that implements Throwable
Throws	It is used in the declaration of the method to illustrate which exceptions are not handled, but rather to be submitted to a higher level of the program.
Transient	Used to indicate that a domain is not part of the serialization of the object. When an object is serialized, the value of the transient variable is not included in the serialized representation, whereas the non-transient variable is included.
True	It's true
Try	Used to define a block that may throw an exception statement. If an exception is thrown, an optional catch statement block will handle the exception thrown in the try statement block. At the same time, a finally statement block is executed, regardless of whether an exception is thrown.
Void	The method declaration in the Java language illustrates that this approach does not have any return value. "Void" can also be used to denote a statement without any function.
Volatile	It is used in the declaration of a variable to indicate that the variable is asynchronously modified by several threads running concurrently.
While	Used to define a looping statement that executes repeatedly. The exit condition of the loop is part of the while statement.

The categories are as follows:

1. Access control: Private protected protected public

2. Class, method, and variable modifiers abstract declares abstract class extends, inherits final ultimate, immutable implements implements interface interface native local new, creates static static Stric TFP Strict, accurate synchronized thread, synchronous transient transient volatile volatile

3. Program Control statement break jumps out of the loop continue continue return returns do run while loop if else inverse for instanceof Instance switch case Returns the result of default in the switch Default

4. Error handling catch handling exception finally there is no exception to execute throw throws an exception object

Throws declares an exception that may be thrown by a try catch exception

5. Package related import into package packages

6. Basic Type Boolean Boolean byte char character type double double float floating-point int integer long Long integer short shorter integer null null true True False

7. Variable reference Super Parent class, superclass this class void no return value

Note: 1. All Java keywords are lowercase 2, goto and const are reserved keywords, not used in Java 3, STRICTFP and volatile is not used; sizeof, then is not a keyword.

4, True,false,null is not the key word in the strict sense, but literals.

(ext: http://www.cnblogs.com/doit8791/archive/2012/05/26/2519545.html)

Java Basic Syntax Summary 1