Java Basics Essay

1. Identifiers: All components of Java require a name. Class names, variable names, and method names are called identifiers.

For the Java identifiers, there are a few things to note:

• All identifiers should start with a letter (A-Z or a-Z), a dollar symbol ($), or an underscore (_).
• Can be a combination of any character after the first character
• Keyword cannot be used as an identifier
• Identifiers are case-sensitive
• Examples of legal identifiers: Age, $salary, _value, __1_value
• Examples of illegal identifiers: 123abc,-salary String (keyword) Java modifier

Like other languages, Java can use modifiers to decorate methods and properties in a class. There are two main types of modifiers:

• Access control modifiers: default, public, protected, private
• Non-access control modifiers: final, abstract, STRICTFP
• Java keywords

  The following is a list of Java reserved words. These reserved words cannot be used for constants, variables, and names of any identifiers.

  Key Words	Description
  Abstract	Abstract methods, modifiers for abstract classes
  Assert	Whether the assertion condition satisfies
  Boolean	Boolean Data types
  Break	Jump out of a loop or label code snippet
  Byte	8-bit Signed data types
  Case	A condition for a switch statement
  Catch	Match with try and catch exception information
  Char	16-bit Unicode character data type
  Class	Defining classes
  Const	Not used
  Continue	Do not execute the remainder of the loop body
  Default	Default branch in the switch statement
  Do	Loop statement, the loop body is executed at least once
  Double	64-bit double-precision floating-point number
  Else	The branch that executes when the IF condition is not established
  Enum	Enum type
  Extends	Represents a class that is a subclass of another class
  Final	Indicates that a value cannot be changed after initialization Indicates that a method cannot be overridden, or that a class cannot have subclasses
  Finally	In order to complete the execution of the code design, mainly for the robustness and integrity of the program, regardless of whether there is no exception to execute code.
  Float	32-bit single-precision floating-point number
  For	For Loop statement
  Goto	Not used
  If	Conditional statements
  Implements	Indicates that a class implements an interface
  Import	Import class
  instanceof	To test whether an object is an instance of a class
  Int	32-bit integer number
  Interface	interface, an abstract type, with only the definition of methods and constants
  Long	64-bit integer number
  Native	Represents methods implemented in non-Java code
  New	Assigning a new class instance
  Package	A series of related classes make up a package
  Private	Represents a private field, or method, etc., accessible only from within the class
  Protected	Indicates that a field can only be accessed through a class or its subclasses Subclasses or other classes within the same package
  Public	Represents a shared property or method
  Return	Method return value
  Short	16-digit number
  Static	Represents a class-level definition that is shared by all instances of the
  Strictfp	Floating-point comparisons use strict rules
  Super	Represents a base class
  Switch	SELECT statement
  Synchronized	A block of code that represents a single thread that can be accessed at the same time
  This	Represents the invocation of the current instance or call another constructor
  Throw	Throw exception
  Throws	Defining exceptions that a method might throw
  Transient	Modify fields that do not serialize
  Try	Represents a code block to do exception handling or a finally mate to indicate whether throwing an exception executes the code in the finally
  void	Tag method does not return any values
  Volatile	Tag fields may be accessed by multiple threads at the same time without synchronizing
  While	While loop

Java Basics Essay