Java Tutorials(the traditional features of the Java, including variables, arrays, data types, operators and control flow)

Language Basics

the traditional features of the Java, including variables, arrays, data types, operators and control flow

Variables

kinds of variables in Java

• Instance Variables(Non-Static Fields)

  Instance Variables are unique to each instance of a object(class), objects store their individual states in "non-statis fields"

• Class Variables(Static Fields)

  Class Variables is governed by the object(class), regardless of how many times the class has been instantiated.

• Local Variables

  A method will often store its temporary state in local variables. Local variables are absolutely only visible to the methods in whhich they are declared,

• Parameters

Primitive Data Types

The Java programming language is statically-typed, which means that all variables must first be declared before they can be used.

Data Type	Default Value(for fields)
byte	0
short	0
int	0
long	0
float	0.0
double	0.0
char	'\u0000'
boolean	false

Local variables are slightly different; the compiler never ever never assgin a default value to an unitialized local variable. You musk make sure assign a local variable a value before you attempt to use it or else result in compile-time error

• Using Underscore Characters in Numeric Literals to Imporve the readability of code.

  Place underscores only between digits. you cannot place underscores in the following places;

   1. At the beginning or end of a number
   2. Adjacent to a decimal point in a floating point literal
   3. Prior to an F or L suffix
   4. In positions where a string of digits is expected

  long creditCardNumber = 1234_6123_2312_2332L; // ✅
  float PI = 3.14_15F; //✅
  float pi = 3_.1415F; //❌
  int x1 = 52_; //❌
  int x2 = Ox_52; //❌
  int x3 = Ox5_2; //❌

Arrays

An array is a container object that holds a fixed number of values of a single type.The length of an array is established when the array is created.

// Create an array of integers with 10 length
int[] anArray = new int[10];
// Create an array with assigned elements
int[] arrInt = {
  100, 200, 300
    400, 500, 600
}

Bullet point

1. The term "instance variable" is another name for non-static field.
2. The term "class variable" is another name for static field.
3. A local variable store termporary state; it is declared inside a method.
4. A variable declared within the openming and closing parenthesis of a method is called a parameter.
5. What are the eight primitive data types supported by the Java programming language? byte，short，int，long，float，double，boolean，char.
6. Character strings are represented by the class java.lang.String.
7. An array is a container object that holds a fixed number of values of a single value.

Operators

Assignment, Arithmetic, and Unary Operators

• The Arithmetic Operators

The languages provides operators that perform addition, subtraction, multiplication, and division.

Operators	Description
+	Additive operator(also used for String concatenation)
-	Subtraction operator
*	Multiplication operator
/	Division operator
%	Remainder operator

• The Unary Operators

The unary operators require only one operand; they perform various operations such as incrementing/decrementing a value by one, negating an expression. or inverting the value of a boolean.

Operator	Description
+	Unary plus operator; indicates positive value
-	Unary minus operator; negates an expression
++	Increment operator; increments a value by 1
--	Decrement operator; decrements a value by 1
!	Logical complement operator; inverts the value of a boolean

• Equality, Relational, and Conditional Operators

Operator	Description
==	equal to
!=	not equal to
>	greater than
>=	greater than or equal to
<	less than
<=	less than or equal to

• The conditional Operators

  • && and || perform Conditional-AND and Conditional-OR operations on two boolean expressions. These operatos exhibit "short-circuiting" behavior.

  • 【expressions ? doSth(T) : doSth(F)】as shorthand for an 【if-then-else】

  Operator	Description
  &&	Conditional-And
  II	Conditional-OR
  ?:	Ternary(shorthand for if-then-else statement)

• Bitwise and Bit Shift Operators

  Operator	Description
  ~	Unary bitwise complement
  <<	Signed left shift
  >>	Signed right shift
  >>>	Unsigned right shift
  &	Bitwise And
  ^	Bitwise exclusive OR
  I	Bitwise inclusive OR