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DefineMainMethod.md

  • Define main entry point
public class Hello {

    public static void main(String [] args){
        
    }
}
  • public
  • static - we need this for java to find the right code
  • void - method wont return anything
  • parameters - what is passed to a function
  • Code is very case sensitive
  • From the right click the green arrow that says run Hello main
  • Gets this output at the bottom:
"C:\Program Files\Amazon Corretto\jdk11.0.10_9\bin\java.exe" "-javaagent:C:\Program Files\JetBrains\IntelliJ IDEA Community Edition 2020.3.2\lib\idea_rt.jar=50747:C:\Program Files\JetBrains\IntelliJ IDEA Community Edition 2020.3.2\bin" -Dfile.encoding=UTF-8 -classpath C:\...\Section3FirstSteps\HelloWorld\out\production\HelloWorld Hello

Process finished with exit code 0
  • 0 is often used to indicate no problem
  • Keep going
  • Type System.out.println("Hello World"); into line 4
  • We have added a statement
    • Complete command to be executed
    • Call method println() and pass it the string "Hello World"
  • Now we have this
public class Hello {

    public static void main(String [] args){
        System.out.println("Hello World");
    }
}
  • Which gives output similar to
"C:\Program Files\Amazon Corretto\jdk11.0.10_9\bin\java.exe" "-javaagent:C:\Program Files\JetBrains\IntelliJ IDEA Community Edition 2020.3.2\lib\idea_rt.jar=50747:C:\Program Files\JetBrains\IntelliJ IDEA Community Edition 2020.3.2\bin" -Dfile.encoding=UTF-8 -classpath C:\...\Section3FirstSteps\HelloWorld\out\production\HelloWorld Hello
Hello World

Process finished with exit code 0