/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public interface People {
	    String whoAmI = "People";
	    void talk();
	}
 
	public static class Human implements People {
		String whoAmI = "Human";
		public void talk() {
		    System.out.println(whoAmI);
		}
    }	
 
    public static class Robot {
    	String whoAmI = "robot";
    	public void talk() {
    		System.out.println(whoAmI);
    	}
    }
 
    public static void startTalk(Human human){
    	human.talk();
    }
 
	public static void main (String[] args) throws java.lang.Exception
	{
		Human human = new Human();
		Robot robot = new Robot();
 
		startTalk(human);
		startTalk(robot); // 에러 발생(error: incompatible types)
 
	}
}

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