A First Program: Hello World!
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Python |
Java |
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The simplest version of
this program consists of a single statement: print("Hello world!")
The PVM simply executes
this statement. Another version embeds
this statement in a main function which is called at the end of the
module: def main(): print("Hello
world!")
main() The PVM executes the
function definition and then calls the function. |
The simplest version of
this program defines a main method within a class: public class
HelloWorld{ static public void
main(String[] args){
System.out.println("Hello world!"); } } The source code defines
but does not call this method.
At program startup, the compiled class HelloWorld is
loaded into the JVM. The JVM
then calls main, which is a class method in HelloWorld. A Java application must
include at least one class that defines a main
method. The byte code file for
this class is the entry point for program execution. |