What is the difference between the JDK and JRE, JVM [?
JDK: Java program compile and run without the JDK environment, the JDK (Java Development Kit) is used to develop a Java application Development Kit, it provides the compilation, the toolkit and resources required for running a Java program,
JRE: is a Java Runtime Environment, refers to the Java Runtime Environment, is a product of Sun and collection of necessary to run a Java application Environment, containing the JVM standard implementation and the Java core class libraries,
The abbreviation of the JVM, the Java Virtual Machine, all of the Java program will be compiled to the first. The class of class files, and in the form of byte code stored in the file,

Java cross-platform principles?
After we write the source code. Java file, need to be explained by the virtual machine implementation, compiled into. A class of binary file, source files compiled into the binary byte code files, virtual machine need the JVM bytecode file interpreted as the platform of the corresponding operation can understand machine code,

The Java API documentation
If there are any problems in the development process, you can find answers in the document, it is indispensable for Java developers, authoritative resources,

Compiling and decompiling
Java source files (.) into a bytecode file (. Class) become the process of compilation, the bytecode (. Class) back to the source file (. Java) process be decompiled,