Jvm Monitoring Tools Linux Part 1




Java Virtual Machine (JVM)
JVM (Java Virtual Machine) is a machine of an imaginary (maya), which works with the likeness of a real application. The JVM provides a hardware specification and platform where Java code compilation occurs. This is the specification that makes Java-based applications be free from any platform because the compilation process is completed by the JVM.

The application of Java programs created with the text file with extension. java. This program produces a compiled bytecode file with extension. one class or more.

Bytecode is a series of machine code instructions similar instructions. The difference is machine code must be run on the computer system where the compilation is addressed, while bytecode runs on the java interpreter is available on all platforms computer systems and operating systems.



Garbage Collection
Many other languages programming examples that allow a programmer to allocate memory at the time it is run. However, after using the memory allocation, there must be a way to put back the memory block so that other programs can use it. In C, C++ and other languages, is the absolute programmer will be responsible for this. This can be difficult when the programmer alpa to return memory blocks causing the situation known as memory leak.

Java program perform garbage collection means that the program does not need to delete your own objects – objects that are no longer used. This facility reduces the burden of managing memory by programmer and reduce or eliminate the source of the biggest mistakes in the language that allows dynamic allocation.

Code Security
Security Code implemented in Java through the use of Java Runtime Environment (JRE). The Java security model uses 3 layers to protect the system from untrusted Java Code.

First, the class-loader handles the loading of the Java classes to a runtime interpreter. This process provides safeguards by separating class – the class that is derived from the local disk with a class – the class that is loaded from the network. This limits the application of a Trojan because class – the class that is derived from the local disk that is loaded first.

Second, the bytecode verifier read bytecode before it is run and guarantee the bytecode meet rules – basic rules of language Java.

Third, security management handles the application level security by controlling whether the program has the right to access resources such as the file system, network ports, external systems and windowing process.

Phase – JAVA programming phase
The first step in the creation of a Java-based program is
writing the program code in the text editor. Example of a text editor that can be used include: notepad, vi, emacs, etc. Program code that is created is then stored in a file with extension. java. After you create and save a program code, compile the file containing the program code using the Java Compiler. The result of the compilation of the berupaberkas bytecode with the extension. class. The file containing the bytecode will then be converted by the Java Interpreter into machine language in accordance with the type and platform being used.




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