How to sort firstname, lastname, age in collections list

[megabull]

I want to sort the elements in the order of firstname, lastname, age. For example, if there are two people with same first name, then the list be sorted by lastname. If both the firstname and lastname are the same, then sorting may be done on the basis of age in ascending order.

import java.util.*;

class Employee implements Comparable<Employee> {

	public String name, Lastname;
	public int age;
	
	 public Employee(String name, String Lastname,int age ){
	     this.name=name;
	     this.Lastname=Lastname;
	     this.age=age;
	 }
	 
	 public String getName(){
		    return name;
		  }
	 public String getLastname(){
		    return Lastname;
		  }
		  public int getAge(){
		    return age;
		  }
	
public int compareTo(Employee obj) {
	Employee e = (Employee)obj;

if(this.name.equals(e.getName()))
	{
		return this.Lastname.compareTo(e.getLastname());
	}
	else
	{
		return this.name.compareTo(e.getName());
	}	
	

}
	
public static void main(String arg[]){

	List<Employee> myList = new ArrayList<Employee>();
myList.add(new Employee("Andrew","Anderson",45));
myList.add(new Employee("Robert","Stalling",22));
myList.add(new Employee("Andrew","Anderson",19));
myList.add(new Employee("Harish","Samtani",45));


for(Employee employee : myList){
	 System.out.println(" "+employee.getName() +" "+employee.getLastname()+ " " + employee.getAge());
}


System.out.println("\nSorting starts now \n");

Collections.sort( myList);
for(Employee employee : myList){
	 System.out.println(" "+employee.getName() +" "+employee.getLastname()+ " " + employee.getAge());
}
}
	 
}

Current output is

Andrew Anderson 45
Robert Stalling 22
Andrew Anderson 19
Harish Samtani 45

Sorting starts now

Andrew Anderson 45
Andrew Anderson 19
Harish Samtani 45
Robert Stalling 22

Any suggestions how to sort in order of age in case both first and last names are a match?

[JosAH]

You're on the right track; you just have to complete your compareTo( ... ) method; something like this:

public int compareTo(Employee that) {
   int result;
   if ((result= this.first.compareTo(that.first)) != 0) return result;
   if ((result= this.last.compareTo(that.last)) != 0) return result;
   return this.age-that.age;
}

kind regards,

Jos

[makpandian]

Awesome code JosAH... Thanks a lot..

[megabull]

@jos : Tried, dint work. My initial code was something like this

int res;
	if(res=(this.name.compareTo(e.getName()))!=0)
    {
        return this.Lastname.compareTo(e.getLastname());
    }
    else
    {
        return this.name.compareTo(e.getName());
    }

It gave a "Unresolved compilation problem:
The operator != is undefined for the argument type(s) boolean, int" issue.

[Tolls]

That code is not the same (structure-wise) as Jos' code above.
Jos does not use the equals() method.

[DarrylBurke]

int res;
if(res = (this.name.equals(e.getName())) != 0)

Use horizontal whitespace for readability (not that it helps very much in this particular code line). See Code Conventions for the Java Programming Language: Contents

What exactly are you trying to compare in that if condition? Why are you trying to assign an int to this.name.equals(e.getName())? Does that method call return an int value?

db

[megabull]

@Tolls : My bad. I had typed the code by modifying the code i posted previously, so missed replacing the equals with compareTo

[megabull]

@Db : Yes,the function returns an integer value (see line 24 of the original post ). What i want to do is that check the int condition after the string condition stops working. I tried the following code, but it failed to work

if(this.name.equals(e.getName()))
	{
		if(this.Lastname.equals(e.getLastname()))
				{
			return (this.age.compareTo(e.getAge()));
				}
		else
			{
			return this.name.compareTo(e.getLastname());
			}
	}
	else
	{
		return this.name.compareTo(e.getName());
	}

It shows the following error

Cannot invoke compareTo(int) on the primitive type int

on the

 return this.age.compareTo(e.getAge()));

line

[megabull]

got it. Declaring as int was the issue. Should have declared it as integer.

[Tolls]

Again, see the code Jos wrote.
That shows what he did for 'age'.

Second, you've a typo (or copy and paste error) on this line:

return this.name.compareTo(e.getLastname());