Java Learning Notes

1. JDK Installation

After the JDK is installed, add system variables.

Variable name: java_home, Variable Value: D:\java\jdk1.7.0, which is the path of the JDK installation just now

Set the CLASSPATH property, variable name: CLASSPATH, Variable value:.; %java_home%\lib\dt.jar;%java_home%\lib\tools.jar; At this point it is important to note that there is a first.;, can't forget,%java_home% represents D:\java\jdk1.7.0 this path

Set the Path property, variable name: path, variable value:%java_home%\bin;%java_home%\jre\bin;, this property is generally there, just add it, pay attention to the problem of semicolons.

When you switch the JDK version, just modify the Java_home variable value.

2. Learn to Masterbasic commands for Java

Commands commonly used in the Java environment are

Javac:java compiler to convert Java source code to bytecode

Java:java interpreter, Bytes executing Java application code from a class file

Appletviewer:java Browser for executing Java applets on HTML files

Javadoc: Used to generate HTML explanatory documents

Jdb:java Debugger

Javah: Generates a C procedure that can invoke a Java procedure, or a header file that can be called by a Java program to a C procedure

The Javap:java disassembler, which displays the accessible features and data in the compiled class file, shows the meaning of the byte code

Jar: Archive and Compress tool, a Java program that merges multiple files into a single jar archive file

Htmlconverter: Command Conversion tool

NATIVE2ASCII: Converting a non-Unicode encoded character file to a Unicode encoded character file

Serialver: Returns SERIALVERUID. Syntax: serialver [show] command option show is used to display a simple interface. Enter the full class name by pressing the ENTER key or the "Show" button to display the Serialveruid.

3.JVM Startup parameter configuration

See Http://zhaohe162.blog.163.com/blog/static/38216797201211431418743/?suggestedreading&wumii

See http://lavasoft.blog.51cto.com/62575/25492/

4.Finally, the difference between final

(1) Final:
A) A class is declared final, meaning that it can no longer derive a new subclass and cannot be inherited as a parent class. Therefore, a class cannot be declared abstract and declared final.
b) The method declaration is final, they will not be changed in use, can only be used, cannot be overloaded.
c) A variable declared as final must be given an initial value at the time of declaration, and can only be read in subsequent references and cannot be modified.
(2) Finally: is a statement that will be executed, written in finally{} inside the statement no matter what happens before, it will certainly execute! Usually used to do some shut-down operations. such as closing database connections, streaming, etc.

5.the construction chain of Java and the order of initialization

Reference http://www.cnblogs.com/miniwiki/archive/2011/03/25/1995615.html

6. Multidimensional arrays

There is actually no multidimensional array in Java, only one-dimensional arrays. A multidimensional array is actually an array of arrays.

7.Object Equal, hashcode, ToString's role

The object object in the equal method, which by default compares two objects with the same reference.

The Obejct object is hashcode so that each object has a default hash value whose value is the object memory storage address.

The ToString method that returns the string for the value of the object.

8.Java dynamic binding mechanism

Insider http://hxraid.iteye.com/blog/428891 of the "doubts" Java dynamic binding mechanism

Java Learning Notes