Sorting an ArrayList

Discussion in 'Java' started by flesh-bound-book, Feb 12, 2010.

  1. flesh-bound-book

    flesh-bound-book

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    [SOLVED] Sorting an ArrayList

    Hey, guys. I have a homework assignment due later tonight and am having a bit of trouble. I have to sort an array list as part of the assignment. My understanding is that must use Collections.sort, but I can't get that to work. I am not sure if that is due to my use of generics or what. Here is my current code.

    Code (Text):
    import java.util.ArrayList;
    import java.util.Collections;

    //create generic MyList class with type parameter T
    final class MyList<T extends Number>{

        //create ArrayList of type T
        ArrayList<T> list = new ArrayList<T>();

        //create an add method that adds argument of type T to ArrayList
        public void add( T new_element ){
        list.add( new_element );
        }

        //create method 'largest' that returns largest value of 'list'
        public T largest(){
        Collections.sort( list );
            //must return largest value after sorting
        }

        //create method 'smallest' that returns smallest value of 'list'
        public T smallest(){
        Collections.sort( list );
        //must return smallest value after sorting
        }
    }

    public final class GenericsHW{

        public static void main(final String[] args) {
        MyList<Number> list = new MyList<Number>();

        list.add( new Integer( 10  ) );
        list.add( new Double( 1.2 ) );
        }

    }
    and the error messages I am getting are:

    Code (Text):
    /MyDev/java/HW3/GenericsHW.java
    /MyDev/java/HW3/GenericsHW.java:30: cannot find symbol
    symbol  : method sort(java.util.ArrayList<T>)
    location: class java.util.Collections
        Collections.sort( list );
                        ^
    MyDev/java/HW3/GenericsHW.java:36: cannot find symbol
    symbol  : method sort(java.util.ArrayList<T>)
    location: class java.util.Collections
        Collections.sort( list );
                        ^
     
    I've looked at quite a few explanations of sorting arraylists, and they all achieve sorting with Collections.sort( ArrayList );, but this isn't working for me. They all used string values for sorting and I am using numbers, but it seems like Collections.sort would be able to sort values of the Number type. Any help would be great. Let me know if I left out something you need to know.
     
    Last edited: Feb 13, 2010
    flesh-bound-book, Feb 12, 2010
    #1
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