Java是一种字节编译语言，目标是一个叫做Java虚拟机的平台，它是基于堆栈的，在许多平台上都有一些非常快速的实现。

用Java编写的代码是:

首先由一个名为javac的程序编译为字节码，如上图左侧所示; 然后，如上图右侧所示，另一个名为java的程序启动java运行时环境，它可以使用java解释器/JIT编译器编译和/或解释字节码。

When does java interpret the bytecode and when does it compile it? The application code is initially interpreted, but the JVM monitors which sequences of bytecode are frequently executed and translates them to machine code for direct execution on the hardware. For bytecode which is executed only a few times, this saves the compilation time and reduces the initial latency; for frequently executed bytecode, JIT compilation is used to run at high speed, after an initial phase of slow interpretation. Additionally, since a program spends most time executing a minority of its code, the reduced compilation time is significant. Finally, during the initial code interpretation, execution statistics can be collected before compilation, which helps to perform better optimization.

Java是一种编译的编程语言，但它不是直接编译为可执行的机器代码，而是编译为一种称为JVM字节代码的中间二进制形式。然后对字节码进行编译和/或解释以运行程序。

Java被编译成字节码，然后进入Java VM，由其解释。

两者都有。首先，java编译(有些人更喜欢说“翻译”)字节码，然后根据JIT的情绪进行编译或解释。

Java是一种字节编译语言，目标是一个叫做Java虚拟机的平台，它是基于堆栈的，在许多平台上都有一些非常快速的实现。