A concept
JDK is the Java language software development kit , mainly used in mobile devices , embedded devices on a java application. JDK entire java development of the core, which contains the JAVA runtime environment ( the JVM + the Java class library system) and JAVA tools.
JDK (Java Development Kit) is a Java language Software Development Kit ( SDK ) .
SE (JavaSE) , Standard Edition , Standard Edition, is a version we usually use, from JDK 5.0 start, changed its name to the Java SE .
EE (JavaEE) , Enterprise Edition , Enterprise Edition, using this JDK develop J2EE applications from JDK 5.0 start, changed its name to the Java EE . From 2018 Nian 2 Yue 26 onwards, the J2EE renamed Jakarta EE [1] .
ME (J2ME) , Micro Edition , is mainly used on mobile devices, embedded devices java applications from JDK 5.0 start, renamed the Java ME .
No JDK , it can not compile Java program (refer to java source .java files), only if you want to run Java programs (refer to class or jar or other archives), to ensure that the appropriate installed the JRE .
two. jdk1.8 new features
Java 8 allows us to interface to add a non-abstract method implementation, just use the default keywords.
Add lambda expressions
Provide functional interfaces
Java 8 allows you to use keywords to delivery method or constructor references
We can directly lambda local variables of the outer expression.
III. Composition
JDK basic components comprising comprising:
javac - compiler, source program converted into bytecode
jar - packaging tools, the packaging-related class files into one file
javadoc - documentation generator, extracted from the source document comments
JDB - Debugger , troubleshooting tools
java - run the compiled java program ( .class suffix)
the appletviewer : applet browser for executing HTML file on Java applets Java browser.
Javah : produce can call Java process C process, or can be established Java program called C header file process.
Javap : the Java disassembler, the display may compile the class file access and data, also shows byte code meaning.
Java: Jconsole tool for system debugging and monitoring
jdk structure of FIG.
IV. Classification
the java.lang : This is the base class systems, such as String are all inside this, the packet can not be introduced into a (Import) on the package can be used.
the java.io : there is class related to all inputs and outputs, such as a file operation.
java.nio : In order to improve io Feature Pack to improve io package performance and write a new package, for example NIO non-blocking application
the java.net : there is network-related classes, such as the URL of , URLConnection and so on.
Classes in java.util : This is the system auxiliary class, especially the collections Collection , List , the Map and so on.
the java.sql : This is the class of database operations, Connection , the Statement , the ResultSet like.
the javax.servlet : This is the JSP , the Servlet such as the use of the class.