如何在终端（Mac）上运行Java程序？

Question

I am new to Java (as of today!) and am trying to run a very simple program in terminal. Normally, when I run a python (still pretty new) program in Terminal I would simple type in "python name.py" in to terminal and it would run. When I type "Java name.java" it does absolutely nothing.

I opened TextWrangler and selected "Run in Terminal" and it returned this error:

"This file doesn't appear to contain a valid 'shebang' line (application error code: 13304)"

My program is named "hello.java" and it contains the code below.

What am I doing wrong?

System.out.println("Hello!");

Answer 1

Open the terminal, go to the directory where the file is located and do this:

javac -classpath . name.java // compile the code
java name                    // run the program

Of course, both javac and java must be available in the operating system's PATH variable, but in a Mac that's already configured.

Answer 2

Type

javac helloworld.java 

java helloworld

The first line calls the compiler and compiles it in the current directory then the next line runs it

Answer 3

"Run in terminal" attempts to run the software as an interpreted script. On UNIX-like systems (meaning almost everything except Windows), a shebang line is used to indicate, what interpreter is to be used. It consists of the characters #! followed by the command to invoke the interpreter (eg #!/usr/bin/python or #!/usr/bin/ruby ). However, Java is not (only) interpreted.

java only runs compiled Java bytecode , so it does not work on source files

Instead, head over to the terminal yourself, compile the code with javac and run the resulting bytecode (the .class files) with java :

javac the_file_name.java
java the_class_name

where the_file_name.java is the file containing main(...) and the_class_name is the name of the class containing main(...) (this should usually be the same as the_file_name )