sorting objects in arraylist in java

[shahidasalavoodeen]

How can I sort objects in an arraylist based on a particular field of the object.
my arraylist has a collection of objects. each object has one of the fields as name. now i want to sort the objects in alphabetical order of names. how do i do dat

[r035198x]

How can I sort objects in an arraylist based on a particular field of the object.
my arraylist has a collection of objects. each object has one of the fields as name. now i want to sort the objects in alphabetical order of names. how do i do dat

If you can control how objects get into the list, you can make sure that the objects get in sorted(insertio n sort). If you already have an unsorted list, then you need to write the sort function to sort that. Are you asking for the sort function?

[r035198x]

This will allow you as many sorts as are compare methods defined for your object:

import java.util.*;
class Church {
	private String name;
	private String pastor;
	public Church(String name, String pastor) {
		this.name = name;
		this.pastor = pastor;
	}
	public String getPastor() {
		return pastor;
	}
	public String getName() {
		return name;
	}
	public void setPastor(String pastor) {
		this.pastor = pastor;
	}
	public String toString() {
		return getName() + " is Pastored by "+getPastor();
	}
	public int compareByPastor(Church c) {
		int x = pastor.compareTo(c.getPastor());
		return x;
	}
	public int compareByName(Church c) {
		int x = name.compareTo(c.getName());
		return x;
	}
}

class Churches {
	private final List<Church> churches;

	public Churches() {
		churches = new ArrayList<Church>();
	}
	public void addWithoutSorting(Church c) {
		churches.add(c);
	}

	//You could always add using this method
	public void addWithSorting(Church c) {

	}
	public void display() {
		for(int j = 0; j < churches.size(); j++) {
			System.out.print(churches.get(j).toString());
			System.out.println("");
		}
   }
   public List<Church> getChurches() {
	   return churches;
   }
   public void sortBy(String s) {
	   for (int i = 1; i < churches.size(); i++) {
		   int j;
		   Church val = churches.get(i);
           for (j = i-1; j > -1; j--) {
			   Church temp = churches.get(j);
			   if(s.equals("Pastor")) {
				   if (temp.compareByPastor(val) <= 0) {
					   break;
				   }
			   }
			   else if(s.equals("Name")) {
				   if (temp.compareByName(val) <= 0) {
				   	   break;
				   }
			   }
			   churches.set(j+1, temp);
			}
			churches.set(j+1, val);
       }
     }

    public static void main(String[] args) {
		Churches baptists = new Churches();
	    baptists.addWithoutSorting(new Church("Pac", "Pastor G"));
	    baptists.addWithoutSorting(new Church("New Life", "Tudor"));
	    baptists.addWithoutSorting(new Church("My Church", "r035198x"));
	    baptists.addWithoutSorting(new Church("AFM", "Cathy"));
	    System.out.println("**********************Before Sorting***********************");
	    baptists.display();
	    baptists.sortBy("Pastor");
	    System.out.println("**********************After sorting by Pastor**************");
	    baptists.display();
	    baptists.sortBy("Name");
	    System.out.println("**********************After sorting by Name****************");
	    baptists.display();

	}

  }