Suddenly there is an idea today, I want to write about my learning process and harvest about myself. Let more Java beginners like me less :) I hope everyone will communicate and support !!!!
Author: Queer Qoo
Java 1st Class ()
Workers must be good, must first take care of them!
What is the program:
1) Input-> Process-> Output
2) Modeling to the real world
What is Java:
Java is not only a language, but also a platform
Development Tools: JDK_1.4.2 Eclipse (a must-choose tool for beginners)
After installing these tools, start the first program example:
The steps are as follows: Edit => Compile => Run
Write the source code with Notepad or other editing tools:
// The source code is as follows.
Public class test {
Public static void main (string [] args) {system.out.println ("Hello, World, I Love Java);}}
Saved as Test.java file after writing, and then
Compilation: Javac Test.java
Run: Java Test
Print Results: Hello, World, I Love Java
First, what is a variable
Variable: memory logo
Name Rules: Digital, Understanding, US Dollar, Unicode Upper
II. Type (strong type)
Boolean (True / Flase)
Char (a letter, a Chinese or any unicode character) 16bit
BYTE value range - 128 to 127
Short-2 ^ 15 to 2 ^ 15-1
INT-2 ^ 31 to 2 ^ 31-1
Long-2 ^ 63 to 2 ^ 63-1
Float 32bit
Double 64bit
// The following source code descriptions The above two points
// Interchange of two variables
Public class test2 {
Public static void main (string [] args) {int a = 5; int b = 7; system.out.println ("a =" a); system.out.println ("b =" b); A = a b; b = ab; a = ab; system.out.println ("a =" a); system.out.println ("b =" b);}}
// maximum and minimum value
Public class test {
Public static void main (string [] args) {system.out.println ("byte:" byte.max_value); system.out.println ("Byte:" byte.min_value; system.out.println (" Short: " short.max_value); System.out.println (" Short: " short.min_value; system.out.println (" byte: Byte.max_Value); system.out.println ("byte: " Byte.max_value; system.out.println (" int: integer.max_value); System.out.println ("INT: Integer.min_Value); System.out.Println (" long: " Long.max_value; system.out.println ("long:" long.min_value); system.out.println ("float:" float.max_value; system.out.println ("float:" float. Min_value; system.out.println ("Double:" doublemax_value); system.out.println ("Double:" double.min_value);}
}
3. Operator
Arithmetic operator: - * /%
Samples:
1 1 = 2 2-1 = 1 2 * 3 = 6 6/2 = 3 3% 5 = 3
Conditional operator: ==! => <> = <=
Relational operator: && || &! | ^ ~
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