无法使用接口的getter方法

Question

I have written below code, just to play with interface, Would you please tell where I have gone wrong here?

This is my interface:

package com.home.intetest;

public interface IFoo {

    public abstract String doWork(String str) throws Exception;

}

This is where I have implemented,

package com.home.intetest;

public class FooImpl implements IFoo {

    @Override
    public String doWork(String str) throws Exception {

        if(str !=null) {
            System.out.println(str);
        }else{
            System.out.println("Wrongggg");
        }

        return str;
    }

}

Now I am trying to call them from main, using getter method, its giving me error,in line where I am using getiFoo method

package com.home.intetest;


public class TestMain {

    private IFoo iFoo;

    public IFoo getiFoo() {
        return iFoo;
    }

    public void setiFoo(IFoo iFoo) {
        this.iFoo = iFoo;
    }


    public static void main(String[] args) {

        String str = "Work method";
        callWorkMethod(str);
    }

    private static void callWorkMethod(String str) {

        String s = getiFoo().doWork(str);

    }

}

Answer 1

1

The line

getiFoo().doWork(str);

can not be called, you need a instance of TestMail first! So boot-up your Application like this:

new TestMain().getiFoo().doWork(str);

2

The error you recieve is a NullPointerException now because iFoo is always null .

Create a instance in the getter using the default constructor like this:

public IFoo getiFoo() {
    if (iFoo == null) {
       iFoo = new FooImpl();
    }
    return iFoo;
}

Or inside the declaration like this:

private IFoo iFoo = new FooImpl();