Can someone explan to me

Question

this method is part of my lab, it should sort words in alphabetical order from
from A to Z . .
i don;t undersatand why did we use .compareTo in this method??
could someone explain what does this method mean
public static void sortList()
          String temp;          
          for(int k = 0; k < count-1; k++)
         for(int p = k+1; p < count; p++)
          if(list[k].compareTo(list[p]) > 0)
                    temp = list[k];
                    list[k] = list[p];
                    list[p] = temp;
}

Answer 1

If all of the elements in a collection implement the Comparable interface, which defines the compareTo method, then the sorting can be done automatically using a TreeSet( ), TreeMap( ), or Collections.sort( ) method. For example:
public class MyClass
implements Comparable
   public int compareTo( Object o )
      if( equals( o ) ) return 0;
      if( o == null ) return -1;
      if( !(o instanceof MyClass) ) throw new ClassCastException( );
      MyClass that = (MyClass)o;
      if( this.getValue( ).lessThan( that.getValue( ) )
          return -1;
      else
          return 1;
public class SomeOtherClass
    public void someMethod( )
        List myClassList = new ArrayList( );
        for( int i = 0; i < 10; i++ ) myClassList.add( new MyClass( ) );
        // Sorts myClassList by casting each element to Comparable
        // and calling compareTo( )
        List sortedList = Collections.sort( myClassList );
}