Null Pointer Exception while using objects as array

Question

This is my EmpData Class:

package com.bank;

public class EmpData {
int id;
String name;
String date;
String pos;
String status;


public void setEmp(int id, String name, String date) {
    this.id = id;
    this.name = name;
    this.date = date;
}

public void setStat(String pos, String stat){
    this.pos = pos;
    this.status = stat;
}

public void disp(){
    System.out.println(id+" : "+name+" : "+date+" : "+pos+" : "+status);
}

}

This is my Main Class:

package com.bank;

public class Bank {
    public static void main(String[] args) {
        EmpData[] obj = new EmpData[4];
        obj[1].setEmp(1, "Test123", "09-04-1990");
        obj[1].setStat("clerk", "on-hold");
        obj[1].disp();
    }
}

i got no syntax error in eclipse, but when i run the program i get the following null pointer error

Exception in thread "main" java.lang.NullPointerException at com.bank.Bank.main(Bank.java:6)

Answer 1

You are not initializing obj[1] before setting values..

as it should be

obj[1] = new EmpData();
obj[1].setEmp(1, "Test123", "09-04-1990");
obj[1].setStat("clerk", "on-hold");
obj[1].disp();

Answer 2

You didn't initialize obj[1], you just allocated 4 slots for EmpData, you create a new instance on each one. Just add this after you create your array:

obj[1] = new EmpData();

Answer 3

Create an instance of EmpData, set data to it and THEN assign it to the desired index. You are trying to assign values to NULL.

Answer 4

You have to fill your array with objects, what you have done is declaring the array and it's size.

public static void main(String[] args) {
        EmpData[] obj = new EmpData[4];
        obj[1] = new EmpData();        
        obj[1].setEmp(1, "Test123", "09-04-1990");
        obj[1].setStat("clerk", "on-hold");
        obj[1].disp();
}

Answer 5

You could also do

for (int i = 0; i < obj.length ; i++) {
    obj[i] = new EmpData();
}

to initialize them all with empty data. You could add a constructor to EmpData so you can set the data on creation of it.

Answer 6

You must first create a new object EmpData [] obj = new EmpData [4]; obj [1] = new EmpData ();

package com.bank;

public class Bank {
    public static void main(String[] args) {
        EmpData[] obj = new EmpData[4];
        obj[1] = new EmpData ();
        obj[1].setEmp(1, "Test123", "09-04-1990");
        obj[1].setStat("clerk", "on-hold");
        obj[1].disp();
    }
}