11th Day Notes

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11th Day Notes

1.java Common development tools

Notepad, Editplus,notepad

A. American Borland company JBuilder C++builder Delphibuilder

Poor scalability, too many errors, expensive

Highly integrated, Jdk,tomcat, highly intelligent development

B. US Sun's own tools NetBeans

Free, open source, operation assignment, running speed is very slow

C. IBM Money development tools, eclipse eclipses

Open source, free, highly scalable

D. MyEclipse added a lot of plugins on eclipse basis

EE, SSH full integration fee

2.eclipse Basic knowledge and operation

A Structure in the working directory after the project is created

SRC--storage is the authoring source file. java

Bin-Stores the compiled class file

B Views and windows in eclipse

B 1 Packageexplorer: Show all the contents of the current project include: Package, class, method, member

B 2 Outline Outline window: Show the entire contents of the current class, with the icon (properties of the Class) do not need to see the specific contents of the class, you can see what is defined in the class

B 3 Restore initialization View--window--Reset

B 4 Eclipse settings

1) Font Size--Window--preferences--gen--app--color and Fonts–java--java Editor–edit

2) Adjust console font--Window--preferences--gen--app--color and fonts---Debug--console font

3) Remove the default comment--Window--preferences--Java--code style--code templates-code, select the content you want to modify, click Edit

4) Remove the mouse hover effect--Window--preferences--Java--editor--hovers--first tick

C Eclipse Shortcut Key Summary

Content Assist Tip: alt+/

Single-line Comment: Ctrl +/Press Uncomment again

Multiline Comment: Check the code you want to comment: Ctrl +shift+/Cancel: ctrl+shift+\

Move the current line: ALT + up and down arrows

Copy current line above or below: ctrl+alt+ up or down

Automatic Guide pack: Ctrl+shift+o

Code formatting: ctrl+shift+f

Comments and suggestions: ctrl+1 handle Red small fork problem

D Code Auto-generation

D 1 Generate Get,set yourself define variable members:

Code blank, right mouse button---source-generate gettter or setter

D 2 Build Constructor Method:

Code blank, right mouse button---source-----generate constructor

E. Import Project

Existing projects, from hard drives, imported into Eclispe

In the Package Explorer, right mouse button, import--general--into workspace

F. Eclipse debugging features, breakpoint debugging

When your program, no errors, run normally, but the results are different from what you think, or run but no results, it is recommended to use the debugging function

Debug mode: Let your program step-by-step execution, see what the results of each move, see the variable

Step: In the valid code, on the left line number, double-click, line number more than a blue dot, this is the breakpoint, when the program runs to this line, automatically stop moving

F5 Single Step into F6 single step execution

F5 can go in the way, F6 straight through the line of code

3. Jar Package

Java is a kind of compressed package, multiple classes of files class, merged into a compressed file, easy to carry, and use, you can directly use the function of the class inside. Later, the database driver Xxx.jar file, Struts Spring Hibernate is all jar files provided

Object class

All classes in Java inherit the object class directly or indirectly.

Class person{}

The person class, there are several methods 12, the parent class object, inherits 11, own constructs

Object class, there are constructor methods, null parameters, maximum permissions, first row no super ()

private static native void Registernatives ();

static{

Registernatives ();}

Native keyword, modifier, local meaning

Methods that are modified by native, non-Java code writing methods, C + + write, function, invoke native operating system functions, no method body, secret, local method, run memory local method stack

4. public int hashcode () returns the hash code value of the object

A. Hash code: The JVM calculates a decimal number based on its own underlying calculation method (hash algorithm)

This number can be understood before the address of the memory of the object

Hashcode method, all subclasses have

B. Public final class GetClass () return value is a class type variable

The class class returns the object

Class is a Description object, class describes the object of the compiled class file

C public string toString () returns the string representation of the object

All subclasses have this method.

In the output statement, the object's ToString method is called by default

The default call to ToString is only called in the output statement, and the other statements do not call

Why the output object, see the class name [email protected]+ address, the object class in source D of the ToString method. Public String toString () {

Return GetClass (). GetName () + "@" +integer.tohexstring (hashcode ()); }

E. GetClass (). GetName () The first method returns the class file object of the runtime class, and the object calls the method GetName gets the name

F. Integer.tohexstring () converts a parameter in a method to a hexadecimal

Hashcode () Simple decimal number

G Purpose, overriding ToString () returns the member variable value, regardless of the static member variable, non-static

If, in a class, there are no member variables, no overriding

H. Operate a variable individually, assign values, or take values, depending on get set

The overridden ToString () outputs the value, and nothing else is done.

I. In SOP statements, when you print an object, you see not the address, the class inherits the object, and the ToString method is overridden

J public boolean equals (Object obj) is used to compare objects, which are compared between objects.

Java engineers believe that all objects have a comparative

K Method source code return this = = obj;

This is a class object that references the obj method parameter and receives the incoming object

Two objects = = when compared, the real address of the memory is compared

General objects are all new, compare objects, the results are generally false

L Override the Equals method to establish how the object compares itself, comparing the values of member variables in the object

M. protected void Finalize () when an object is in heap memory, after it becomes garbage

The JVM initiates a garbage collection period, collects this object, and, when charged, invokes the object's, Finalize method

Finalize final finally

11th Day Notes