Structuring Data with Java - Java - page 270

trieve the obvious components from the collection. The following program uses a TreeSet to
sort some names:

// A TreeSet keeps objects in sorted order. Use a Comparator
// published by String for case-insensitive sorting order.
TreeSet < String > theSet = new new TreeSet <>( String . CASE_INSENSITIVE_ORDER );

theSet . add ( "Gosling" );
theSet . add ( "da Vinci" );
theSet . add ( "van Gogh" );
theSet . add ( "Java To Go" );
theSet . add ( "Vanguard" );
theSet . add ( "Darwin" );
theSet . add ( "Darwin" ); // TreeSet is Set, ignores duplicates.

System . out . printf ( "Our set contains %d elements" , theSet . size ());

// Since it is sorted we can easily get various subsets
System . out . println ( "Lowest (alphabetically) is " + theSet . first ());

// Print how many elements are greater than "k"
// Should be 2 - "van Gogh" and "Vanguard"
System . out . println ( theSet . tailSet ( "k" ). toArray (). length +
" elements higher than \"k\"" );

// Print the whole list in sorted order
System . out . println ( "Sorted list:" );
theSet . forEach ( name -> System . out . println ( name ));

One last point to note is that if you have a Hashtable or HashMap , you can convert it to a
TreeMap , and therefore get it sorted, just by passing it to the TreeMap constructor:

TreeMap sorted = new TreeMap(unsortedHashMap);

Finding an Object in a Collection

Problem

You need to see whether a given collection contains a particular value.