Array of Object

future3839

Hi, I have define the following class in my practice.

package array;
public class Student {

// definition of fileds
private int studentId= 0;
private String name;
private String family;

//definition of constructor
public Student(int \_studentId, String \_name, String \_family){
    studentId= \_studentId;
    name= \_name;
    family= \_family;
}

//definition of methods
public int getStudentId(){
    return studentId;
}
public void setStudentId(int newStudentId){
    studentId= newStudentId;
}

public String getName(){
        return name;
}
public void setName(String newName){
    name= newName;
}

public String getFamily(){
    return family;
}
public void setFamily(String newFamily){
    family= newFamily;
}

}

then in main class I have these code

package array;
import java.io.*;
import array.Student;
public class Main {

public static void main(String\[\] args) {
    //define Array of Object(Student's Class)
    Student\[\] st = new Student\[3\];
    st\[0\]= new Student(3400,"XXX", "YYY");
    st\[1\]= new Student(3800, "ZZZ", "WWW");
    st\[2\]= new Student(4200,"RRR", "MMM");

    System.out.println(st\[1\]);
    System.out.println("\\n");
}

}

the problem is after I run the program nothing print out on the screen. is there problem in code??

shivamkalra

st[1] is object of type Student, not a String. You should have toString() method within your Student class

public String toString()
{
return "Name: " + name + ", " + family + " ID:" + studentId + "
}

Than use simply use

System.out.println(st[1].toString());

It will start printing the student information.

jschell

Shivamkalra wrote:

st[1] is object of type Student, not a String

Which wouldn't stop it from using the default toString() method which would print something.

jschell

future3839 wrote:

System.out.println(st[1]);

Presumably you are using the standard Sun/Oracle VM. If not then you need to specify what you are using. Modify this line so it prints something such, for example. System.out.println("student 1= " + st[1]); There are two possibilities. 1. Your program still prints nothing. Thus you are not running the code you think you are. 2. It prints the text but not else. That suggests you have a toString() method in the class that prints nothing.

Lost User

If I run your code I get the following output:

testing.BaseTest$Student@1ad77a7

However, If I take Shivamkalra's advice and add a ToString() method to the Student class such as:

public String toString()
{
return "Name: " + name + ", " + family + " ID:" + studentId + "
}

I get the following output:

Name: ZZZ, WWW ID:3800

I must get a clever new signature for 2011.

TorstenH

perfect answer! @ future3839 just a short note: your code looks really good, clean and well structured. One small point I noticed is the package declaration: package array;. It would be more appropriate to use a longer declaration like package au.future3839.school.arrays;. this would define your package clearly as your package, otherwise you could get into trouble when having a lucky hit on a predefined package. regards Torsten

I never finish anyth...

shi fj

st[1] is a object,not primitive type.So it need a print method. :) from china