showing null pointer exception with junit test case

Question

i am trying to sort the employee object based on salary using the junit test case.

it is my employee sort class

package day4;
import day4.Employee;
public class EmployeesInfoWithSalary {
    private Employee[] employee;
    private int numberOfEmployees;
public EmployeesInfoWithSalary(Employee[] employee, int numberOfEmployees) {
    super();
    this.employee = employee;
    this.numberOfEmployees = numberOfEmployees;
}

public Employee[] getSortBasedOnSalary() {

    String temp;
    for (int iterator = 0; iterator < numberOfEmployees; iterator++) {
        int minSalary = employee[iterator].getSalary();
        int index = iterator;
        for (int comparator = iterator; comparator < numberOfEmployees; comparator++) {
            if (employee[comparator].getSalary() < minSalary) {
                index = comparator;
                minSalary = employee[comparator].getSalary();
            }

        }

        employee[index].setSalary(employee[iterator].getSalary());
        employee[iterator].setSalary(minSalary);
        temp = employee[index].getId();
        employee[index].setId(employee[iterator].getId());
        employee[iterator].setId(temp);
        temp = employee[index].getName();
        employee[index].setName(employee[iterator].getName());
        employee[iterator].setName(temp);

    }

    return employee;

}

}

employee object class is as follows

package day4;

public class Employee {

private String id;
private String name;
private int salary;

public String getId() {
    return id;
}

public void setId(String id) {
    this.id = id;
}

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

public int getSalary() {
    return salary;
}

public void setSalary(int salary) {
    this.salary = salary;
}

}

testemployee salary class for junit test case is as follows

package day4;

import static org.junit.Assert.*;
import day4.Employee;

import org.junit.Test;

public class TestEmployeeInfoWithSalary {

@Test
public void testGetSortBasedOnSalary() {

Employee[] employee = new Employee[5];

employee[0].setName("pratap");
employee[1].setName("aruna");
employee[2].setName("satyam");
employee[3].setName("krishna");
employee[4].setName("siva");

employee[0].setId("k0100");
employee[1].setId("k0101");
employee[2].setId("k0102");
employee[3].setId("k0103");
employee[4].setId("k0104");
employee[0].setSalary(10000);
employee[1].setSalary(1000);
employee[2].setSalary(8000);
employee[3].setSalary(6000);
employee[4].setSalary(9000);
EmployeesInfoWithSalary employeeInfoWithSalary= new EmployeesInfoWithSalary(employee, 5);

employee[4].setName("pratap");
employee[0].setName("aruna");
employee[2].setName("satyam");
employee[1].setName("krishna");
employee[3].setName("siva");

employee[4].setId("k0100");
employee[0].setId("k0101");
employee[2].setId("k0102");
employee[1].setId("k0103");
employee[3].setId("k0104");
employee[4].setSalary(10000);
employee[0].setSalary(1000);
employee[2].setSalary(8000);
employee[1].setSalary(6000);
employee[3].setSalary(9000);
assertArrayEquals(employee,employeeInfoWithSalary.getSortBasedOnSalary());

}

}

the log is showing the error that null point expression..

can any body help me.. thanks..

I suggest you read the NullPointerException to see where it occurred and use your debugger to try to debug the code to determine why this is happening. — Peter Lawrey
– Peter Lawrey, Commented Aug 29, 2012 at 12:55
Why not use an ArrayList rather than an Array and then use Collections.sort() and use a custom comparator. That would simplify things quite a lot I think — RNJ
– RNJ, Commented Aug 29, 2012 at 12:55
Is this homework? Don't use arrays, use java.util.List (java.util.ArrayList). If you must use arrays, passing a number of elements in the array to your constructor is not necessary since there's a length field on the array objects (you can find out the number of elements from employee.length). — maksimov
– maksimov, Commented Aug 29, 2012 at 12:58
You know, if you want to sort a list of Employees you could just implement a compareTo method that works based on the salaries and then use Arrays.sort(..). — arshajii
– arshajii, Commented Aug 29, 2012 at 13:00

Peter Lawrey · Accepted Answer · 2012-08-29 12:57:03Z

7

I suspect this is the line of the NPE.

// creates an array full of null values.
Employee[] employee = new Employee[5];

employee[0].setName("pratap");

You need to add Employee objects to each element in the array.

A better approach is to use a constructor which takes all the needed fields.

Employee[] employee = {
    new Employee("pratap", "k0100", 10000),
    new Employee("aruna",  "k0101",  1000),
    new Employee("satyam", "k0102",  8000),
    new Employee("krishna","k0103",  6000),
    new Employee("siva",   "k0104",  9000) };

answered Aug 29, 2012 at 12:57

Peter Lawrey

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2 Comments

Pratap M Over a year ago

I get the answer by doing like this......Employee firstEmployee=new Employee(); firstEmployee.setName("pratap"); firstEmployee.setSalary(10000); firstEmployee.setId("k0100"); employee[0]=firstEmployee; firstEmployee.setSalary(1000); firstEmployee.setId("k0101"); firstEmployee.setName("aruna"); employee[1]=firstEmployee;

Peter Lawrey Over a year ago

Try printing System.out.println(Arrays.toString(employee)); at various points or stepping through the code in your debugger. This will allow you to see what is happening.

Amit Deshpande · Accepted Answer · 2012-08-29 13:05:08Z

0

After

 Employee[] employee = new Employee[5];

for each index in array you need to initialize Employee object.

 employee[0] = new Employee(); etc

answered Aug 29, 2012 at 13:05

Amit Deshpande

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