1- Do you recommend reading Java language specification ?
2- I have very week knowledge about System Programming, I want to know how java internally works, furthermore ,sometimes I donot understand what is written in javadoc when some system programming involved in the method or class describtion, so please tell me books and/or tutorails to read about System Programming in java, or something sounds like "java from inside to outside"
1. You'll probably learn a lot about the details of Java if you read the JLS, but I wouldn't recommend it if you are very new to Java and you just want to learn the concepts. I've never read it completely myself, but occasionally I use it to lookup things.
2. If you want to learn how Java works internally, then you could look at the source code of the standard API which you will find in the file src.zip in your JDK installation directory. It contains the Java part of the sources. If you really want to know everything, you can even get the complete JDK 5.0 source code (see the download page).
IF you really mean that you want to learn the internals at the CPU level, then "Inside the Java Virtual machine" may be what you want. Although the book is several years old the guts of the JVM have not changed that much.