Question

 import java.util.*;
 import java.io.*;

public class LootGenerator{

public static void main (String[] args)
    throws FileNotFoundException{
        System.out.println("This program simulates the random item generator");
        System.out.println("from the game Diablo II.  Happy hunting!");
        System.out.println();
        String file="monstats.txt";
        Monster[] array = getArray(file);
        //Monster alex=getRandomMonster(array);
        }

public Monster getRandomMonster(Monster[] array){
  int randMonster = (int)(Math.random() * array.length);
    return array[randMonster];
}

public Monster[] getArray (String file)
    throws FileNotFoundException{
Scanner sc = new Scanner (new File (file));
Monster[] array = new Monster[sc.nextInt()];
sc.next(); //takes away the word Class
sc.next(); //takes away the word Type
sc.next(); //takes away the word Level
sc.next(); //takes away the word TreasureClass
for(int a = 0; a < array.length; a++)
{
    array[a] = new Monster(sc.next(), sc.next(), sc.nextInt(), sc.next());
}
return array;
}

}

  class Monster{
    private String monsterClass;
private String type;
    private int level;
    private String treasureClass;

public Monster(String myClass, String myType, int myLevel, String myTreasureClass){
    monsterClass = myClass;
      type = myType;
    level = myLevel;
    treasureClass = myTreasureClass;
}

public String getMonsterClass(){
    return monsterClass;
}

public String getType(){
    return type;
}

public int getLevel(){
    return level;
}

public String getTreasureClass(){
    return treasureClass;
}

}

I can’t figure out what is wrong with my program…any advice? I keep getting that it can’t be referenced from a static context – the line Monster[] array = getArray(file) that is. The object of the program is to randomly generate a monster from a text file – the assignment is here if you need to look at the text file itself: http://www.cis.upenn.edu/~cis110/hw/hw06/index.html

Answer 1

You’re trying to call a regular method from a static method, which isn’t possible. You could instantiate LootGenerator and then call the method or make the method static (simply add the static modifier to the method).

One solution:

public static void main (String[] args)
    throws FileNotFoundException {
        System.out.println("This program simulates the random item generator");
        System.out.println("from the game Diablo II.  Happy hunting!");
        System.out.println();
        String file = "monstats.txt";
        LootGenerator lg = new LootGenerator();
        Monster[] array = lg.getArray(file);
        Monster alex = lg.getRandomMonster(array);
}

You can find more information about instance and class members here.

In short, instance methods can only be called on instances of a class. Static methods belong to the class and can be called from anywhere, but they can’t access instance variables or call instance methods unless they actually have a reference to an instance of a class.