collections.sort overriding compare to

/*
   running main method produces the following output:
 
       original list:[a1, b1, c2, x3, x1, y5, z4, c2]
        dups removed:[a1, b1, c2, x1, x3, y5, z4]
    dup ints removed:[a1, c2, x3, z4, y5]
 dup Strings removed:[a1, b1, c2, x1, y5, z4]
 
*/
 
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;
 
 
public class RemoveWhileIterating {
    List<Foo> foos = new ArrayList<Foo>();
    
    RemoveWhileIterating(Foo[] foos) {
        this.foos.addAll( Arrays.asList( foos )) ;
    }
   
    void removeDups() {
        SortFoosByString comparator = new SortFoosByString();
        Collections.sort(foos,comparator);
        Foo prev = null ;
        for ( Iterator<Foo> itr = foos.iterator(); itr.hasNext();  ) {
            Foo foo = itr.next();
            if ( prev != null ) {
                if ( comparator.compare(prev, foo) == 0  ) {
                    itr.remove();
                }
            }
            prev = foo;
        }
    }
 
    void removeDupStrings() {
        Collections.sort(foos,new SortFoosByString());
        String prev = null;
        for ( Iterator<Foo> itr = foos.iterator(); itr.hasNext();  ) {
            Foo foo = itr.next();
            if ( foo.s.equals(prev) ) {
                itr.remove();
            }
            prev = foo.s;
        }
    }
    void removeDupInts() {
        Collections.sort(foos,new SortFoosByNumber());
        boolean first = true;
        int prev = 0;
        for ( Iterator<Foo> itr = foos.iterator(); itr.hasNext();  ) {
            Foo foo = itr.next();
            if ( first ) {
                first = false;
            }
            else {
                if ( prev == foo.n ) {
                    itr.remove();
                }
            }
            prev = foo.n;
        }
    }
    public static void main(String[] args) {
        Foo[] testFoos = new Foo[] { new Foo("a",1), new Foo("b",1), new Foo("c",2), 
                new Foo("x",3), new Foo("x",1), new Foo("y",5), new Foo("z",4), new Foo("c",2)};
        
        System.out.printf("%20s:%s\n","original list",Arrays.asList(testFoos));
        RemoveWhileIterating test;
        
        test = new RemoveWhileIterating(testFoos);
        test.removeDups();
        System.out.printf("%20s:%s\n","dups removed",test.foos);
        
        test = new RemoveWhileIterating(testFoos);
        test.removeDupInts();
        System.out.printf("%20s:%s\n","dup ints removed",test.foos);
        
        test = new RemoveWhileIterating(testFoos);
        test.removeDupStrings();
        System.out.printf("%20s:%s\n","dup Strings removed",test.foos);
        
    }
}
 
class Foo  {
    String s;
    int n ;
    public Foo(String s, int n) {
        super();
        this.s = s;
        this.n = n;
    }
    public String toString(){
        return s+n;
    }
}
 
class SortFoosByNumber implements Comparator<Foo> {
 
    @Override
    public int compare(Foo o1, Foo o2) {
        if ( o1.n != o2.n ) {
            return o1.n - o2.n ;
        }
        return o1.s.compareTo(o2.s);
    }
    
}
 
class SortFoosByString implements Comparator<Foo> {
 
    @Override
    public int compare(Foo o1, Foo o2) {
        if ( o1.s.compareTo(o2.s)!= 0 ) {
            return o1.s.compareTo(o2.s);
        }
        return o1.n - o2.n;
    }
   
}

                                              

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