calling another method from the main method in java

Question

I have   class foo      public static void main String   args         do             public void do           but then when I call do   from main by running the command java foo on the command line  java complains that you can t call a method from a static function   So my question is  How do you call methods from the main method and if it is not possible what are some alternative strategies to call methods after the program is run from the command line using the java command

User · Answer

Check out for the static before the main method, this declares the method as a class method, which means it needs no instance to be called. So as you are going to call a non static method, Java complains because you are trying to call a so called "instance method", which, of course needs an instance first ;)

If you want a better understanding about classes and instances, create a new class with instance and class methods, create a object in your main loop and call the methods!

 class Foo{

    public static void main(String[] args){
       Bar myInstance = new Bar();
       myInstance.do(); // works!
       Bar.do(); // doesn't work!

       Bar.doSomethingStatic(); // works!
    }
 }

class Bar{

   public do() {
   // do something
   }

   public static doSomethingStatic(){
   }
}

Also remember, classes in Java should start with an uppercase letter.

User · Answer

This is a fundamental understanding in Java  but can be a little tricky to new programmers   Do a little research on the difference between a static and instance method   The basic difference is the instance method do   is only accessible to a instance of the class foo   You must instantiate  create an instance of  the class  creating an object  that you use to call the instance method   I have included your example with a couple comments and example   public class SomeName      this is a static method and cannot call an instance method without a object public static void main String   args           can t do this from this static method  no object reference        someMethod           create instance of object     SomeName thisObj   new SomeName          call instance method using object     thisObj someMethod         instance method public void someMethod        System out print  some message              end class SomeName

User · Answer

First java will not allow you to have do   method  Instead you can make it doOperation     Second You cann t invoke directly non static methods from static function  Main is a static function  You need to instantiate the class first and then invoke method using that instance   Third you can invoke static method directly from non static methods

User · Answer

You can only call instance method like do    which is an illegal method name  incidentally  against an instance of the class   public static void main String   args     new Foo   doSomething       public void doSomething       Alternatively  make doSomething   static as well  if that works for your design

User · Answer

You can do it multiple ways  Here are two  Cheers   package learningjava   public class helloworld       public static void main String   args            new helloworld   go               OR         helloworld get               public void go            System out println  Hello World              public static void get            System out println  Hello World  Again

User · Answer

If you want to use do    in your main method there are 2 choices because one is static but other  do    not   Create new instance and invoke do   like new Foo   do    make static do   method   Have a look at this sun tutorial

[java] calling another method from the main method in java

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