Java SE Development Kit(JDK7)

JDK is the core of the entire Java, including the Java Runtime Environment (Java Runtime Envirnment), a bunch of Java tools and the basic Java class library (rt.jar). No matter what Java application server is, it actually has a certain version of JDK built-in. Therefore, mastering JDK is the first step to learn Java well. The most mainstream JDK is the JDK released by Sun. Among them, the JVM (Java Virtual Machine) included in IBM's JDK is much more efficient than the JVM included in Sun JDK. Jrocket, which specifically runs on the x86 platform, is much more efficient on the server side than Sun JDK. But no matter what, we still need to master Sun JDK first.
Among them, the JVM (Java Virtual Machine) included in IBM's JDK runs much more efficiently than the JVM included in Sun JDK. And Jrocket, which specifically runs on the x86 platform, also runs much more efficiently on the server side than Sun JDK. But no matter what, , we still need to master Sun JDK first.
The most important command line tools of the JDK:
java: Start JVM to execute class
javac: Java compiler
jar: Java packaging tool
javadoc: Java documentation generator
You must be very, very familiar with these command lines and be proficient in each parameter. For learning these commands, there are detailed documents on the JDK Documentation.
From a beginner's perspective, using JDK to develop Java programs can quickly understand the relationship between the various parts of the code in the program, which is helpful for understanding Java's object-oriented design ideas. Another notable feature of JDK is that it upgrades with the upgrade of Java (J2EE, J2SE and J2ME) versions. But its shortcomings are also very obvious, that is, it is very difficult to develop large-scale enterprise-level Java applications, cannot carry out complex Java software development, and is not conducive to group collaborative development.
The Java language is probably the first choice for network application languages. This is all due to its high degree of security and cross-platform features. You can see Java on almost all current computer platforms. In the past, many people may have complained that although Java has quite good cross-platform and security protection features, its execution speed is far lower than that of various traditional programming languages ​​such as C++.