Java的帮助！ 实现某个对象的二维数组，该对象具有多个私有数据类型和对象

Question

I'm trying to make a 2d array of an object in java. This object in java has several private variables and methods in it, but won't work. Can someone tell me why and is there a way I can fix this? This is the exeception I keep getting for each line of code where I try to initialize and iterate through my 2d object.

"Exception in thread "main" java.lang.NullPointerException at wumpusworld.WumpusWorldGame.main(WumpusWorldGame.java:50) Java Result: 1"

Here is my main class:

public class WumpusWorldGame {

    class Agent {

        private boolean safe;
        private boolean stench;
        private boolean breeze;

        public Agent() {
            safe = false;
            stench = false;
            breeze = false;
        }

    }

    /**
     * @param args
     *            the command line arguments
     * @throws java.lang.Exception
     */
    public static void main(String [] args) {
        // WumpusFrame blah =new WumpusFrame();
        // blah.setVisible(true);

        Scanner input = new Scanner(System.in);

        int agentpts = 0;
        System.out.println("Welcome to Wumpus World!\n ******************************************** \n");

//ArrayList<ArrayList<WumpusWorld>> woah = new ArrayList<ArrayList<WumpusWorld>>();

        for (int i = 0 ; i < 5 ; i++) {

            WumpusWorldObject [] [] woah = new WumpusWorldObject [5] [5];

            System.out.println( "*********************************\n Please enter the exact coordinates of the wumpus (r and c).");
            int wumpusR = input.nextInt();
            int wumpusC = input.nextInt();

            woah[wumpusR][wumpusC].setPoints(-3000);
            woah[wumpusR][wumpusC].setWumpus();
            if ((wumpusR <= 5 || wumpusC <= 5) && (wumpusR >= 0 || wumpusC >= 0)) {
                woah[wumpusR][wumpusC].setStench();
            }
            if (wumpusC != 0) {
                woah[wumpusR][wumpusC - 1].getStench();
            }
            if (wumpusR != 0) {
                woah[wumpusR - 1][wumpusC].setStench();
            }
            if (wumpusC != 4) {
                woah[wumpusR][wumpusC + 1].setStench();
            }
            if (wumpusR != 4) {
                woah[wumpusR + 1][wumpusC].setStench();
            }

            System.out.println( "**************************************\n Please enter the exact coordinates of the Gold(r and c).");
            int goldR = input.nextInt();
            int goldC = input.nextInt();
            woah[goldR][goldC].setGold();
            System.out.println("***************************************\n How many pits would you like in your wumpus world?");
            int numPits = input.nextInt();
            for (int k = 0 ; k < numPits ; k++) {
                System.out.println("Enter the row location of the pit");
                int r = input.nextInt();
                System.out.println("Enter the column location of the pit");
                int c = input.nextInt();
                woah[r][c].setPit();
                if ((r <= 4 || c <= 4) && (r >= 0 || c >= 0)) {
                    woah[r][c].setBreeze();
                }
                if (c != 0) {
                    woah[r][c - 1].setBreeze();
                }
                if (r != 0) {
                    woah[r - 1][c].setBreeze();
                }
                if (c != 4) {
                    woah[r][c + 1].setBreeze();
                }
                if (r != 4) {
                    woah[r + 1][c].setBreeze();
                }
            }
            for (int x = 0 ; x < 4 ; x++) {
                int j = 0;
                while (j < 4) {
                    agentpts = agentpts + woah[x][j].getPoints();
                    Agent [] [] k = new Agent [4] [4];

                    if (woah[x][j].getWumpus() == true) {
                        agentpts = agentpts + woah[x][j].getPoints();
                        System.out.println("You just got ate by the wumpus!!! THE HORROR!! Your score is " + agentpts);
                    }
                    if (woah[x][j].getStench() == true) {
                        k[x][j].stench = true;
                        System.out.println("You smell something funny... smells like old person.");
                    }
                    if (woah[x][j].getBreeze() == true) {
                        k[x][j].breeze = true;
                        System.out.println("You hear a breeze. yeah");
                    }
                    if (woah[x][j].getPit() == true) {
                        agentpts = agentpts + woah[x][j].getPoints();
                        System.out.println("AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAH! you dumb bith, your dead now.");
                    }
                    // if breeze or stench, if breeze and stench, if nothing, etc then move.
                    k[x][j].safe = true;
                    // if(k[i][j].isSafe()!=true){

                    // } else { }
                }
            }
        }
    }
}

Here is my class object that I'm trying to implement:

package wumpusworld;

/**
 *
 * @author Jacob
 */

public class WumpusWorldObject {
private boolean stench;
private boolean breeze;
private boolean pit;
private boolean wumpus;
private boolean gold;
private int points;
private boolean safe; 

public WumpusWorldObject(){   
}
    public boolean getPit() { 
      return pit;
    }

    public void setPit() {
        this.pit = true;
    }

    public boolean getWumpus() {
        return wumpus;
    }

    public void setWumpus() {
        this.wumpus = true;

    }

    public int getPoints() {
        return points;
    }

    public void setPoints(int points) {
        this.points = points;
    }
    public boolean getStench() {
        return stench;
    }

    public void setStench() {
        this.stench = true;
    }

    public boolean getBreeze() {
        return breeze;
    }

    public void setBreeze() {
        this.breeze = true;
    }

    public boolean getSafe() {
        return safe;
    }

    public void setSafe() {
        this.safe = true;
    }
    public void setGold(){
        this.gold=true;
    }
}

Answer 1

Creating array doesn't mean it will be automatically filled with new instances of your class. There are many reasons for that, like

• which constructor should be used
• what data should be passed to this constructor.

This kind of decisions shouldn't be made by compiler, but by programmer, so you need to invoke constructor explicitly.

After creating array iterate over it and fill it with new instances of your class.

for (int i=0; i<yourArray.length; i++)
    for (int j=0; j<yourArray[i].length; j++)
        yourArray[i][j] = new ...//here you should use constructor 

Answer 2

AClass[][] obj = new AClass[50][50];

is not enough, you have to create instances of them like

obj[i][j] = new AClass(...);

In your code the line

woah[wumpusR][wumpusC].setPoints(-3000);

must be after

woah[wumpusR][wumpusC] = new WumpusWorldObject();

.