显示带有junit测试用例的空指针异常

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..

Answer 1

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) };

Answer 2

After

 Employee[] employee = new Employee[5];

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

 employee[0] = new Employee(); etc