Member Avatar for sarathsshanker

//ArrayListEx(main class)

import java.io.*;
import man.Phone;
import man.Person;
import java.util.*;

public  class ArrayListEx{

public static void main(String[] args){

Person p= new Person();
p.setName("yo");
ArrayList<Phone> pList = new ArrayList<Phone>();
Phone ph = new Phone();
ph.setOne("dasd");
pList.add(ph);
System.out.println("sgs "+pList);
}
}

My Program has a Person,Phone and ArrayListEx(main class) classes,Person contains an ArrayList<Phone> class but when printing the List of Phone from Person,the result is the address of the element instead of the actual element.

//Result:
sgs [man.Phone@4830c221]

Thanks.

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  • Latest Post Latest Post by sarathsshanker

Dani AI

Generated

and are right that the fix lives in toString. One extra detail that helps: when you print a List, it builds its output by calling toString on each element. So if Phone knows how to describe itself, your ArrayList will print cleanly.

// Phone.java
public class Phone {
  private String one;

  public String getOne() { return one; }
  public void setOne(String one) { this.one = one; }

  @Override
  public String toString() {
    return one == null ? "<phone: unset>" : one;
  }
}

If you cannot (or do not want to) alter Phone, format the output at the call site by selecting the field you care about.

// Java 8+
String phones = pList.stream()
    .map(Phone::getOne)
    .collect(java.util.stream.Collectors.joining(", ", "[", "]"));
System.out.println("sgs " + phones);
// Works on older Java
StringBuilder sb = new StringBuilder("[");
for (int i = 0; i < pList.size(); i++) {
  if (i > 0) sb.append(", ");
  sb.append(pList.get(i).getOne());
}
sb.append("]");
System.out.println("sgs " + sb.toString());

A couple of small hygiene tips while you are here: keep fields private, add @Override above toString to catch signature typos, and consider returning an unmodifiable view from Person.getPhoneList() if you do not want callers to mutate it. These tweaks make debugging output predictable and your model classes safer to use.

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All 4 Replies

Member Avatar for NormR1

man.Phone@4830c221

What you printed was the String returned by the Phone class's default toString() method. It is made of the full classname, @ and the object's hashcode(in hex).
If you want to change that String, you need to override the Phone class's toString() method and have it return the String with what you want to see printed.

Member Avatar for sarathsshanker

but i did not assign a toString method to the Phone class,this is the Phone class:

package man;

import java.io.*;



public class Phone{

public String one;



public String getOne(){
return one;

}
public void setOne(String one)
{
this.one = one;

}


}

and this is the Person class:

ackage man;


import java.io.*;
import man.*;
import java.util.*;


public class Person{

public String name;
public ArrayList<Phone> ph= new ArrayList<Phone>();



public void setPhoneList(ArrayList<Phone> ph){
this.ph= ph;
}

public ArrayList<Phone> getPhoneList(){
return ph;

}

public String getName(){

return name;
}

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

}
Member Avatar for JamesCherrill

Every Java class inherits a toString() method from the Object class, so methods like println use that to convert the object you want to print into a String. The inherited method prints the class name and the object's hash (normally the same as its address). If you want to display something more helpful, override the toString method in your class to return a useful string. Eg

class Person {
    private String givenName, familyName;
    ...
    public String toString() {
        return "Person: " + givenName + " " + familyName;
    }

You should do this for every class you create so when you print an instance you get useful output.

Member Avatar for sarathsshanker

Thanks,I understand...and it works.

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