Java，将字符串从一个类传递到另一个类

Question

In below code i'm doing somthing wrong. Sorry if this is a bit basic. I get this working fine if it's all in the one class but not when i break the classes up like in the code below:

class Apples{
    public static void main(String[] args){

        String bucket = "green"; //instance variable

        Apples appleOne = new Apples(); //create new object (appleOne) from Apples class

        System.out.println("Paint apple one: " + appleOne.paint(bucket));
        System.out.print("bucket still filled with:" + bucket);

        }//end main

    }//end class

class ApplesTestDrive{

    public String paint(String bucket){

        bucket = "blue"; //local variable
        return bucket;

        }//end method

    }//end class

Error Message:

location:class Apples
cannot find symbol
pointing to >> appleOne.paint(bucket)

Any hints?

Answer 1

You need to create an instance of ApplesTestDrive , not Apples . The method is in there.

So, instead of

Apples appleOne = new Apples();

do

ApplesTestDrive appleOne = new ApplesTestDrive();

This has nothing to do with passing by reference (so I removed the tag from your question). It's just a programmer error (as practically all compilation errors are).

Answer 2

You are calling the method paint on Apple object BUT the paint method is in AppleTestDrive class.

Use this code instead:

AppleTestDrive apple = new AppleTestDrive();
apple.paint(bucket);

Answer 3

System.out.println("Paint apple one: " + appleOne.paint(bucket)); paint is a method of ApplesTestDrive class and appleOne is an Apples objject, so you can't call appleOne.paint here.