How to add the objects to the arraylist class if object has many states

[upanshu vaid]

Hi,
In this below code I want to do that once I set the state of the object I want to add that object to the arraylist

import java.util.ArrayList;
import java.util.Scanner;
public class Sort_Using_Comparable {
    public static void main(String[] args) {
        ArrayList<String> ar=new ArrayList<String>();
  Sort [] s=new Sort[3];
Scanner scan=new Scanner(System.in);
 for(Sort s1:s)
{
s1=new Sort();
  System.out.println("enter the name ");
String k=  scan.next();
s1.setName(k);
System.out.println("enter the age ");
int k1=  scan.nextInt();
s1.setAge(k1);
System.out.println("enter the sex ");
String k2=  scan.next();
s1.setSex(k2);
System.out.println("name="+s1.getName()+"age="+s1.getAge()+"Sex="+s1.getSex());
System.out.println(s1.toString());
}
    }
  }
class Sort{
    private String name;
    private String sex;
    private int age;
       public  String toString()
{
return name+"\n"+age+"\n"+sex;
}
 public void setName(String name )
{
this.name=name;
}
public String  getName()
{
return this.name;
}
public String getSex() {
        return sex;
    }
    public void setSex(String sex) {
        this.sex = sex;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
 }

kindly help on this

[K. Tsang]

Your line 5 should have read

ArrayList<Sort> ar = new ArrayList<Sort>(); // instead of String

Then after you have got the inputs after line 19, add the "sort" to the array list ar.

Don't know why you will need an array (line 6) and a list (line 5) given the list is Sort type.

[upanshu vaid]

Thanks for your reply
one more quick ?

import java.util.ArrayList;
import java.util.Collections;
import java.util.Scanner;
public class Sort_Using_Comparable   {
    public static void main(String[] args) {
        ArrayList<Details> ar=new ArrayList<Details>();
  Details [] s=new Details[3];
DetailsImpl d1=new DetailsImpl();
  Scanner scan=new Scanner(System.in);
 for(Details s1:s)
{
s1=new Details();
  System.out.println("enter the name ");
String k=  scan.next();
s1.setName(k);
System.out.println("enter the age ");
int k1=  scan.nextInt();
s1.setAge(k1);
System.out.println("enter the sex ");
String k2=  scan.next();
s1.setSex(k2);
ar.add(s1);
}
 Collections.sort(ar);
System.out.print("Sorting according to age"+ar+"\n");
 Collections.sort(ar,d1);
System.out.print("Sorting according to name"+ar+"\n");    
   Collections.sort(ar,d1);
System.out.print("Sorting according to sex"+ar+"\n");
    }
  }
class Details implements Comparable<Details> {
    private String name;
    private String sex;
    private int age;
    Integer age1;
       public  String toString()
{
return name+"\t"+age+"\t"+sex;
}
 public void setName(String name )
{
this.name=name;
}
public String  getName()
{
return this.name;
}
public String getSex() {
        return sex;
    }
    public void setSex(String sex) {
        this.sex = sex;
    }
    public Integer getAge() {
        return age1;
    }
    public void setAge(int age) {
     this.age = age;
        age1=this.age;
    }
    public int compareTo(Details o) {
     return  age1.compareTo(o.getAge());
       }
   }

comparator class

import java.util.*;
public class DetailsImpl implements Comparator<Details> {
    public int compare(Details o1, Details o2) {
           int name=  o1.getName().compareTo(o2.getName());
   int sex=o1.getSex().compareTo(o2.getSex());
   return name;
   }    
   }

How can I make comparator to sort according to and according to sex

[upanshu vaid]

How can I make comparator to sort according to name and according to sex

[K. Tsang]

You want to compare name THEN sex or either name or sex?

If either, then you need 2 comparators one for each. If both, then check if names are equals then check sex.

if (name1.equals(name2)) {
return sex1.compareTo(sex2);
} else {
return name1.compareTo(name2);
}

[Winston Gutkowski]

upanshu vaid wrote:How can I make comparator to sort according to name and according to sex

You were a whisker away from it with the comparator you just wrote, but then you returned 'name'.

As K.Tsang said, if you want to order by name THEN sex, then the sex comparison only needs to be done if the names are equal.

The problem is that, for any Comparable object, there are TWO ways of determining if they are "equal":
1. equals() returns true.
2. compareTo() returns 0.
And there is nothing that requires that the two methods work the same (although it's usually a good idea if they do).

Since your Comparator is creating an order, it makes sense to me to use compareTo(), since it is the method that provides an order; so putting all that together, you get (from your own method):

public int compare(Details o1, Details o2) {
   int name = o1.getName().compareTo(o2.getName());
   if (name == 0)
      return o1.getSex().compareTo(o2.getSex())
   else
      return name;
}

or something very like it.

See how close you were?

Winston