other notes about Java Collection

entrySet() , values() and keySet()

import java.util.Iterator;
import java.util.Map.Entry;
import java.util.TreeMap;

public class mapTest{
	public static void main(String [] args){
		
		TreeMap<String , Integer> map = new TreeMap<String ,Integer>();
		map.put("a", 1);
		map.put("b", 2);
		map.put("c", 3);
		map.put("d", 4);
		
		// values()
		Iterator<Integer> iter1 = map.values().iterator();
		while(iter1.hasNext()){
			System.out.print(iter1.next() + "	");
		}
		System.out.println();
		
		//entrySet()
		Iterator<Entry<String,Integer> >iter2 = map.entrySet().iterator();
		Entry<String,Integer > one;
		while(iter2.hasNext()){
			one = iter2.next();
			System.out.print(one.getKey()+":"+one.getValue()+ "	");
		}
		System.out.println();
		
		// keySet()
		Iterator<String> iter3 = map.keySet().iterator();
		while(iter3.hasNext()){
			System.out.print(iter3.next()+ "	");
		}
		System.out.println();
		
	}
}

Difference between List and Set

• List can contain two items that have common value , while Set can't .
• Sort Method :
  -- List : Collections.sort(list , ...);
  -- Set : new TreeSet ( new Comparator() {...} )