Java Primary knowledge

• Standard input and output for Java:
  Output:

  System.out.print ();
  System.out.println (); More Print a carriage return
  System.out.println ("Xiao Liu Liu");
  System.out.println ("Xiao Wang Wang");

Input:

Import Java.util.Scanner;
Scanner Scanner = new Scanner (system.in);//Input Object
Scanner.close ();//Close Scanner
Scanner.nextint ();//integral type for absorbing inputs
Scanner.next ();//Absorbing strings
Scanner.nextboolean ();//Absorbing Boolean type
Scanner.nextbyte ();//absorption byte type
Scanner.nextdouble ();//absorbing double precision type
Scanner.nextfloat ();//absorption single precision type
Scanner.next (). charAt (0);//Absorbing single characters
Scanner.nextshort ();//absorbing short-integer
Scanner.nextlong ();//absorption of long plastic

• 　　　　

  Constant
  1. Integer Constants 123
  2. Decimal constant 1.23
  3. Boolean (Boolean)-type constant true
  4. Character constant ' 1 '
  5. String constant "123 Plan on Time"
  6.NULL constant NULL
  

  Variable
  Why use variables
  --memory address is not easy to remember, reuse, convenient operation
  To define the format of a variable
  --Variable name of data type = initialization value;
  Identifier naming rules
  --First character: letter, underscore, ' $ ' (cannot start with a number)
  --The rest: numbers, letters, underscores, ' $ ' (-NO)

  
  java keyword (reserved word)
  The Java language has 51 keywords and cannot use reserved keywords to name classes, methods, or variables
  Data type
  boolean int long short byte float double Char class interface
  Process Control
  If else do and for switch case default break continue return try Catch finally
  Modifier
  Public protected private final void static STRICTFP abstract transient synchronized volatile native
  Operation
  Package import throw throws extends implements this super instanceof new
  Other
  True false NULL Goto const

• Import Other projects

  Import->general->existing Projects into workspace
  Select the extracted project catalog->finish

Java Primary knowledge