Please! Need some help here!

Question

public class NobleHouse
    private String names;
    private int maxno;
    private Knight[] knight;
    public NobleHouse(String names,int maxno)
        this.names=names;
        this.maxno=maxno;
        knight=new Knight[maxno];
    public String getHouseName()
        return names;
    public int getCurrentKnights()
        return maxno;
    public Knight getBestKnight()
        Knight max=knight[0];
        for(int i=1;i<getCurrentKnights();i++)
            if(knight.getSkill()>max.getSkill())
max=knight[i];
return null;
public Knight getKnightByName(String names)
for(int i=0;i<getCurrentKnights();i++)
if (knight[i].equals(names))
return knight[i];
return null;
public Knight getNextKnight()
int next=0;
next++;
if(getCurrentKnights() == next)
next=0;
return knight[next];
public void addKnight(Knight next)
int i;
for(i=0;i<getCurrentKnights();i++)
if(next!=null && i<getCurrentKnights())
next=new Knight(next.getName(),next.getJousts(),next.getVictories());
knight[i]=next;
next.setHouseName(names);
public void printKnights()
          if(knight[0]==null)
               System.out.println("Emty House");
else
for(int i=0;i<getCurrentKnights();i++)
System.out.println(knight[i].getName());
import java.util.*;
import java.text.*;
public class Knight
    private String name,type;
    private int joust,victories;
    public Knight(String name,int joust,int victories)
        type="Freelance";
        this.name=name;
        this.joust=joust;
        this.victories = victories;
    public String getHouseName()
        return type;
    public void setHouseName(String housename)
        type=housename;
    public String getName()
        return name;
    public int getJousts()
        return joust;
    public int getVictories()
        return victories;
    public String getRank()
        String a="Squire";
        String b="Knight";
        String c="Kings Chapion";
        if(joust<20 && joust>0)
            return a;
        else
            if(joust>20 && joust<40)
                return b;
        return c;
    public double getBaseSkill()
        double ratio;
        double totalvictory=getVictories()*getVictories();
        double totaljoust=getJousts()*getJousts();
        double total=totalvictory/totaljoust;
        ratio=Math.sqrt(total);
        return ratio;
    public int getSkill()
        int number=0;
        if(getRank()=="Squire")
          number=(int) (100*getBaseSkill()*1);
        else
            if(getRank()=="Knight")
               number=(int) (100*getBaseSkill()*1.5);
           else
                if(getRank()=="Kings Chapion")
                   number=(int) (100*getBaseSkill()*2);
        return number;
    public void incrementJousts(boolean won)
        joust++;
        if(won==true)
            victories++;
    public boolean joust(boolean won)
        Random no = new Random();
        won=false;
        int knit1=no.nextInt(250)+getSkill();
        int knit2=no.nextInt(250)+getSkill();
        if(knit1>knit2)
            won=true;
        incrementJousts(won);
        return won;
    public void print()
        DecimalFormat ft=new DecimalFormat("0.#");
        System.out.println("Knights name: "+getName());
        System.out.println("Knights rank: "+getRank());
        System.out.println("House name: "+getHouseName());
        System.out.println("Knights skill: "+ft.format(getSkill()));
public class HouseTest
     public static void main(String [] args)
        //Create teh NobleHouse object to test...
          NobleHouse nh = new NobleHouse("Round Table", 3);
          //Now test the methods...
          System.out.println("TEST : printKnight() on empty set...");
        System.out.println("TEST : (Should say that the house is empty)");
          nh.printKnights();
          System.out.println();
        System.out.println("TEST : addKnight() then calling printKnights()...");
        System.out.println("TEST : (Should print Gwain)");
          nh.addKnight(new Knight("Gwain", 10, 10));
          nh.printKnights();
          System.out.println();
        System.out.println("TEST : getKnightByName() on Gwain...");
        System.out.println("TEST : (Should print Gwains details again)");
        Knight k = nh.getKnightByName("Gwain");
        k.print();
        System.out.println();
          System.out.println("TEST : Adding another Knight...");
          nh.addKnight(new Knight("Lancalot", 40, 40));
        nh.printKnights();
        System.out.println();
        System.out.println("TEST :  getNextKnight()...");
        System.out.println("TEST : (Should print \"gwain, lanc, gwain, lanc\")");
        k = nh.getNextKnight();
        k.print();
        k = nh.getNextKnight();
        k.print();
        k = nh.getNextKnight();
        k.print();
        k = nh.getNextKnight();
        k.print();
        System.out.println();
        System.out.println();
        System.out.println("TEST : Adding one more Knight...");
        nh.addKnight(new Knight("Friday", 25, 20));
        nh.printKnights();
        System.out.println();
        System.out.println("TEST : getBestKnight() (should be Lancelot)...");
          k = nh.getBestKnight();
        k.print();
}I have no error when compiled but when i run the program don't give me the correct result ! (Exception in thread "main" java.lang.NullPointerException)
I think something is wrong at the addKnight() method of the NobleHouse class!
Any idear how to fix it and what is wrong in there????! sothe program will give me the correct result! Thank

Answer 1

see if this works
import java.util.*;
import java.text.*;
class NobleHouse
    int next = 0;
    private String names;
    private int maxno;
    private Knight[] knight;
    int currentKnights = 0;
    public NobleHouse(String names,int maxno)
        this.names=names;
        this.maxno=maxno;
        knight=new Knight[maxno];
    public String getHouseName(){return names;}
    public int getCurrentKnights(){return currentKnights;}
    public Knight getBestKnight()
        Knight max=knight[0];
        for(int i=1;i<getCurrentKnights();i++)
            if(knight.getSkill()>max.getSkill())
max=knight[i];
return max;
public Knight getKnightByName(String names)
for(int i=0;i<getCurrentKnights();i++)
if (knight[i].getName().equals(names))
return knight[i];
return null;
public Knight getNextKnight()
next++;
if(getCurrentKnights() == next)
next=0;
return knight[next];
public void addKnight(Knight next)
int i;
for(i=0;i<maxno;i++)
if(knight[i] == null)
knight[i]=new Knight(next.getName(),next.getJousts(),next.getVictories());
knight[i].setHouseName(names);
currentKnights++;
break;
public void printKnights()
if(knight[0]==null) System.out.println("Emty House");
else for(int i=0;i<getCurrentKnights();i++) System.out.println(knight[i].getName());
class Knight
private String name,type;
private int joust,victories;
public Knight(String name,int joust,int victories)
type="Freelance";
this.name=name;
this.joust=joust;
this.victories = victories;
public String getHouseName(){return type;}
public void setHouseName(String housename){type=housename;}
public String getName(){return name;}
public int getJousts(){return joust;}
public int getVictories(){return victories;}
public String getRank()
String a="Squire";
String b="Knight";
String c="Kings Chapion";
if(joust<20 && joust>0) return a;
else if(joust>20 && joust<40) return b;
return c;
public double getBaseSkill()
double ratio;
double totalvictory=getVictories()*getVictories();
double totaljoust=getJousts()*getJousts();
double total=totalvictory/totaljoust;
ratio=Math.sqrt(total);
return ratio;
public int getSkill()
int number=0;
if(getRank()=="Squire")
number=(int) (100*getBaseSkill()*1);
else
if(getRank()=="Knight") number=(int) (100*getBaseSkill()*1.5);
else if(getRank()=="Kings Chapion") number=(int) (100*getBaseSkill()*2);
return number;
public void incrementJousts(boolean won)
joust++;
if(won==true) victories++;
public boolean joust(boolean won)
Random no = new Random();
won=false;
int knit1=no.nextInt(250)+getSkill();
int knit2=no.nextInt(250)+getSkill();
if(knit1>knit2) won=true;
incrementJousts(won);
return won;
public void print()
DecimalFormat ft=new DecimalFormat("0.#");
System.out.println("Knights name: "+getName());
System.out.println("Knights rank: "+getRank());
System.out.println("House name: "+getHouseName());
System.out.println("Knights skill: "+ft.format(getSkill()));
class HouseTest
public static void main(String [] args)
NobleHouse nh = new NobleHouse("Round Table", 3);
System.out.println("TEST : printKnight() on empty set...");
System.out.println("TEST : (Should say that the house is empty)");
nh.printKnights();
System.out.println();
System.out.println("TEST : addKnight() then calling printKnights()...");
System.out.println("TEST : (Should print Gwain)");
nh.addKnight(new Knight("Gwain", 10, 10));
nh.printKnights();
System.out.println();
System.out.println("TEST : getKnightByName() on Gwain...");
System.out.println("TEST : (Should print Gwains details again)");
Knight k = nh.getKnightByName("Gwain");
k.print();
System.out.println();
System.out.println("TEST : Adding another Knight...");
nh.addKnight(new Knight("Lancalot", 40, 40));
nh.printKnights();
System.out.println();
System.out.println("TEST : getNextKnight()...");
System.out.println("TEST : (Should print \"gwain, lanc, gwain, lanc\")");
k = nh.getNextKnight();
k.print();
k = nh.getNextKnight();
k.print();
k = nh.getNextKnight();
k.print();
k = nh.getNextKnight();
k.print();
System.out.println();
System.out.println();
System.out.println("TEST : Adding one more Knight...");
nh.addKnight(new Knight("Friday", 25, 20));
nh.printKnights();
System.out.println();
System.out.println("TEST : getBestKnight() (should be Lancelot)...");
k = nh.getBestKnight();
k.print();