Java Basics for Beginners to learn Java notes

Source: Internet
Author: User

The first time to learn Java, some basic common shortcuts and some very basic knowledge points (the notes are scattered more chaotic)

Java is an object-oriented and cross-platform language, namely: Write once, run anywhere;

Java not only applies to stand-alone applications and web-based programs, but also to create attachment programs for consumer devices, such as mobile phones, handheld devices, and more.

Java Naming conventions
The initials can be letters, underscores ' _ ', ' $ ' symbols
followed by any number of numbers, letters, underscores, ' $ ' symbols
Usually the first letter is lowercase and the first letter of the word is capitalized. Example: Myscore

MyEclipse Programming Java Code Shortcuts (Novice does not recommend the use of MyEclipse and other development integration tools, preferably using EditPlus or Notepad to write code)

Ctrl+l Chack

Ctrl+o Search Method
Ctrl+shift+r Check Class

Alt+shift+s F Format Specification collation
Ctrl+shift+f

CTRL + A Select all
ctrl+/notes
ctrl+shift+/ctrl+shift+\ Comment Paragraph

alt+/Quick Completion

Ctrl+shift+o Quick Guide Package

Basic data type:
Numeric type: Int (+) short (+) long (+) double (+) float (+) byte
Non-numeric: char (+) Boolean

int to String intger.valueof
int to double automatic type promotion
double to int (int) + variable coercion type conversion

The difference between break and continue
Application: Break can be used in switch structure and loop structure; Continue can only be used in loop structure
function (in loop structure): Break statement terminates a loop, the program jumps to the next statement outside the loop block;
Once you encounter the Continue keyword, the code after continue is no longer executed and goes directly to the next loop

Array

Error: Array subscript out of bounds Java.lang.arrayindexoutofboundsexception:4

for (int i = 0; i < c.length; i + = 2)//take array subscript as an even number, cycle efficiency problem

Tri-Wood operation
(Logical judgment)? (The result is true): (the result is false)

Scattered knowledge points
Random random = new random ();


= = compares the memory address
Equals is the value of the comparison variable "male". Equals ()

Switch cannot pass in a double type (a talent of more than 1.7 versions)

If else is more suitable for interval selection, switch is more suitable for single target value

Precision Drift Bigdecimal.valueof

DecimalFormat format=new decimalformant ("#.00") retain two decimal places

Compiler Error Run error logic error code specification Fault tolerant mechanism readable simplicity redundancy


/+ * + Enter comment on method called method comment or dynamic comment Check method body ALT + SHIFT + J

/* * for text comment

Ctrl+shift+i viewing the value of a variable

F6 debugging the next line, F8 debugging the next breakpoint, F5 into the current method, F7 jump out of the current method to return to the previous layer

A foreach loop, I is the value of the subscript at each loop, I equals a[1] or a[n]
When you can determine the number of cycles, use a For loop,

Write Java program ideas: Think good ideas, define variables, write logic down, encapsulate

Java Basics for Beginners to learn Java notes

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