My First In Java

javac.exe. This is the compiler of java.
What does a compiler do? Compiler checks the syntax or formats of the codes you have written on a java program. It will ensure that all the words you have written comply with the java statement commands. If errors are detected from your program, it will specify the line number on where the mistake/s took place. You need to correct those errors, and re-compile. You will only proceed on the next stage of the development if your program is error-free.

Figure C1.1 Phases of Java program
An error-free program compiled by the javac.exe produces a byte code file. Byte code is a machine-language codes that will be interpreted by a Java Virtual Machine (JVM). The codes are no longer expressed in a human language but with the codes the machine understands. Byte code file has an extension filename of .class. An example on how to compile a program in a command line is as follows (Hello is the name of the program):
javac Hello.java
3. Run. Along with the downloads of JDK is an interpreter called java.exe. An interpreter is used to serve as an interface so the processor of the machine can understand what your program wants to achieve once you run it. Please note that the byte code file (filename with the .class extension) is the one interpreted and not the original file you have written (filename with the .java extension). Below is an example on how to run a java byte code program on a command line:
java Hello

Role of IDE
Integrated Development Environment (IDE) is a software tool