Getting NullPointerException on calling getter method

Question

I am having three classes StudentMain, StudentService, Student. Student class contains getters and setters method and from StudentMain I'm passing Student object to StudentService. Below is the code:

code for StudentMain:

public class StudentMain {
static Student data [] = new Student[4];
static { for (int i = 0; i < data.length; i++) 
    data [i] =new Student();
    data [0] = new Student ("Sekar", new int [] {35, 35, 35}); 
    data [1] = new Student(null,new int[]{11,22,33});
    data [2] = null; 
    data [3] = new Student ("Manoj", null);

}
public static void main(String[] args) {
    // TODO Auto-generated method stub
    StudentService studentService = new StudentService ();
    System.out.println ("Number of Objects with Marks array as null =" + studentService.findNumberOfNullMarks (data));
    System.out.println ("Number of Objects with Name as null="+ studentService.findNumberOfNullNames(data));
    System.out.println ("Number of Objects that are entirely null="+ studentService.findNumberOfNullObjects(data));
    }

}

code for Student:

public class Student {
private String name;
private int marks[];
public void setName(String name) {
    this.name=name;
}
public String getName() {
    return name;
}
public void setMarks(int [] marks) {
    this.marks=marks;
}
public int[] getMarks() {
    return marks;
}
public Student() {

}
public Student(String name,int[] marks) {
    setName(name);
    setMarks(marks);
}

}

code for StudentService:

public class StudentService{
Student[] data;
public int findNumberOfNullMarks(Student data[]) {
    this.data=data;
    int count=0;
    int i=0;
    while(i!=data.length) {
        if(data[i].getMarks()==null)
            count++;
        i++;
    }
    return count;
}
public int findNumberOfNullNames(Student data[]) {
    int count=0;
    int i=0;
    while(i!=data.length) {
        if(data[i].getName()==null)
            count++;
        i++;
    }
    return count;
}
public int findNumberOfNullObjects(Student data[]) {
    int count=0;
    int i=0;
    while(i!=data.length) {
        if(data[i]==null)
            count++;
        i++;
    }
    return count;
}

}

I am getting exception at if(data[i].getMarks()==null) and if(data[i].getMarks()=null) in StudentService class.

score 0 · Accepted Answer · answered Mar 10 '19 at 14:10

data [0] = new Student ("Sekar", new int [] {35, 35, 35}); 
data [1] = new Student(null,new int[]{11,22,33});
data [2] = null; 
data [3] = new Student ("Manoj", null);

for i = 0, data[0] having object and having array marks in object so you will not get java.lang.NullPointerException

for i = 1, data[1] having object and having array marks in object so you will not get java.lang.NullPointerException

for i = 2, data[2] having null so you will get java.lang.NullPointerException

for i = 3, data[3] having having object but array marks is null so you will get java.lang.NullPointerException

So you need to make sure you should have object and array.

Getting NullPointerException on calling getter method

1 Answers1