<div dir="ltr" style="text-align: justify;" trbidi="on">
<pre class="highlight" name="code">public class TreeSet<;E>; 
extends AbstractSet<;E>; 
implements NavigableSet<;E>;, Cloneable, Serializable 
</pre>
<p>A <i><b>NavigableSet </b></i>implementation based on a <i><b>TreeMap</b></i>. The elements are ordered using their natural ordering, or by a <i><b>Comparator </b></i>provided at set creation time, depending on which constructor is used.</p>
<p> This implementation provides guaranteed <b><i>log(n)</i></b> time cost for the basic operations (<b>add, remove and contains)</b>.</p>
<p> Note that the ordering maintained by a set (whether or not an explicit comparator is provided) must be consistent with equals if it is to correctly implement the <i><b>Set </b></i>interface. This is so because the <i><b>Set </b></i>interface is defined in terms of the equals operation, but a <i><b>TreeSet </b></i>instance performs all element comparisons using its <i><b>compareTo (or compare)</b></i> method, so two elements that are deemed equal by this method are, from the standpoint of the set, equal. The behavior of a set is well-defined even if its ordering is inconsistent with equals; it just fails to obey the general contract of the <i><b>Set </b></i>interface. </p>
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<p><b>Note that this implementation is not synchronized. </b>If multiple threads access a tree set concurrently, and at least one of the threads modifies the set, it must be synchronized externally. This is typically accomplished by synchronizing on some object that naturally encapsulates the set. If no such object exists, the set should be &#8220;wrapped&#8221; using the <b><i>Collections.synchronizedSortedSet</i></b> method. This is best done at creation time, to prevent accidental unsynchronized access to the set:</p>
<pre class="highlight" name="code">SortedSet s = Collections.synchronizedSortedSet(new TreeSet(...)); 
</pre>
<p><i><b>TreeSet </b></i>provides an implementation of the <b><i>Set </i></b>interface that uses a tree for storage. Objects are stored in sorted, ascending order. Access and retrieval times are quite fast, which makes <i><b>TreeSet </b></i>an excellent choice when storing large amounts of sorted information that must be found quickly. </p>
<div class="separator" style="clear: both; text-align: center;"><img border="0" src="https://dineshonjava.com/wp-content/uploads/2013/05/treeset.jpg"/></div>
<p>
 The <i><b>TreeSet </b></i>class supports four <i><b>constructors</b></i>. The first form constructs an empty tree set that will be sorted in ascending order according to the natural order of its elements:</p>
<pre class="highlight" name="code">TreeSet( ) 
//The second form builds a tree set that contains the elements of c. 
TreeSet(Collection c) 
 
//The third form constructs an empty tree set that will be sorted according to the comparator specified by comp. 
TreeSet(Comparator comp) 
 
//The fourth form builds a tree set that contains the elements of ss: 
TreeSet(SortedSet ss) 
</pre>
<p><b>Methods in <i>TreeSet</i>:</b></p>
<table class="src">
<tbody>
<tr>
<th>SN</th>
<th>Methods with Description</th>
</tr>
<tr>
<td>1</td>
<td><i><b>void add(Object o)</b></i><br />
Adds the specified element to this set if it is not already present.</td>
</tr>
<tr>
<td>2</td>
<td><i><b>boolean addAll(Collection c) </b></i><br />
Adds all of the elements in the specified collection to this set.</td>
</tr>
<tr>
<td>3</td>
<td><i><b>void clear() </b></i><br />
Removes all of the elements from this set.</td>
</tr>
<tr>
<td>4</td>
<td><i><b>Object clone()</b></i><br />
Returns a shallow copy of this TreeSet instance.</td>
</tr>
<tr>
<td>5</td>
<td><i><b>Comparator comparator()</b></i><br />
Returns the comparator used to order this sorted set, or null if this tree set uses its elements natural ordering.</td>
</tr>
<tr>
<td>6</td>
<td><b><i>boolean contains(Object o)</i> </b><br />
Returns true if this set contains the specified element.</td>
</tr>
<tr>
<td>7</td>
<td><i><b>Object first() </b></i><br />
Returns the first (lowest) element currently in this sorted set.</td>
</tr>
<tr>
<td>8</td>
<td><i><b>SortedSet headSet(Object toElement)</b></i><br />
Returns a view of the portion of this set whose elements are strictly less than toElement.</td>
</tr>
<tr>
<td>9</td>
<td><i><b>boolean isEmpty() </b></i><br />
Returns true if this set contains no elements.</td>
</tr>
<tr>
<td>10</td>
<td><i><b>Iterator iterator() </b></i><br />
Returns an iterator over the elements in this set.</td>
</tr>
<tr>
<td>11</td>
<td><i><b>Object last() </b></i><br />
Returns the last (highest) element currently in this sorted set.</td>
</tr>
<tr>
<td>12</td>
<td><i><b>boolean remove(Object o) </b></i><br />
Removes the specified element from this set if it is present.</td>
</tr>
<tr>
<td>13</td>
<td><i><b>int size() </b></i><br />
Returns the number of elements in this set (its cardinality).</td>
</tr>
<tr>
<td>14</td>
<td><i><b>SortedSet subSet(Object fromElement, Object toElement) </b></i><br />
Returns a view of the portion of this set whose elements range from fromElement, inclusive, to toElement, exclusive.</td>
</tr>
<tr>
<td>15</td>
<td><i><b>SortedSet tailSet(Object fromElement) </b></i><br />
Returns a view of the portion of this set whose elements are greater than or equal to fromElement.</td>
</tr>
</tbody>
</table>
<p>
<b>Example of <i>TreeSet </i>class:</b><br />
The following program illustrates several of the methods supported by this collection:</p>
<pre class="highlight" name="code">import java.util.*; 
 
public class TreeSetDemo { 
 
 public static void main(String args[]) { 
 // Create a tree set 
 TreeSet ts = new TreeSet(); 
 // Add elements to the tree set 
 ts.add("C"); 
 ts.add("A"); 
 ts.add("B"); 
 ts.add("E"); 
 ts.add("F"); 
 ts.add("D"); 
 System.out.println(ts); 
 } 
} 
</pre>
<p><b>output:</b></p>
<div class="separator" style="clear: both; text-align: center;"><img border="0" src="https://dineshonjava.com/wp-content/uploads/2013/05/treeset.png" /></div>
<p>
<b>Example of <i>TreeSet </i>adding duplicate value:</b></p>
<pre class="highlight" name="code">import java.util.*; 
 
public class TreeSetDemo { 
 
 public static void main(String args[]) { 
 // Create a tree set 
 TreeSet ts = new TreeSet(); 
 // Add elements to the tree set 
 ts.add("Dinesh"); 
 ts.add("Anamika"); 
 ts.add("Sweety"); 
 ts.add("Anamika"); 
 ts.add("Sweety"); 
 ts.add("Raj"); 
 System.out.println(ts); 
 } 
} 
</pre>
<p><b>output:</b></p>
<div class="separator" style="clear: both; text-align: center;"><img border="0" src="https://dineshonjava.com/wp-content/uploads/2013/05/treeset2.png"/></div>
<p></p>
<div style="background-color: #f2f9fc; border-radius: 3px; border: 1px solid #c9e6f2; line-height: 1.45; padding: 16px;">
<b>Java Collections Tutorial</b></p>
<ol style="text-align: left;">
<li><b><a href="https://dineshonjava.com/arraylist-class-in-java-collection/">ArrayList class</a></b></li>
<li><b><a href="https://dineshonjava.com/linkedlist-class-in-collection/">LinkedList class</a></b></li>
<li><b><a href="https://dineshonjava.com/listiterator-interface-in-collection/">ListIterator interface</a></b></li>
<li><b><a href="https://dineshonjava.com/hashset-class-in-collection/">HashSet class</a></b></li>
<li><b><a href="https://dineshonjava.com/linkedhashset-class-in-collection/">LinkedHashSet class</a></b></li>
<li><b><a href="https://dineshonjava.com/difference-between-hashset-and-treeset/">Difference between TreeSet &; HashSet</a></b></li>
<li><b><a href="https://dineshonjava.com/map-interface-in-collection/">Map interface</a></b></li>
<li><b><a href="https://dineshonjava.com/hashmap-class-in-collection-framework/">HashMap class</a></b></li>
<li><b><a href="https://dineshonjava.com/how-does-java-hashmap-work-internally/">How does work HashMap?</a> </b></li>
<li><b><a href="https://dineshonjava.com/difference-between-treemap-vs-hashmap/">Difference between TreeMap vs HashMap</a></b></li>
<li><b><a href="https://dineshonjava.com/linkedhashmap-class-in-collection/">LinkedHashMap class</a></b></li>
<li><b><a href="https://dineshonjava.com/treemap-class-in-collection-framework/">TreeMap class</a></b></li>
<li><b><a href="https://dineshonjava.com/hashtable-class-in-collection-framework/">Hashtable class</a></b></li>
<li><b><a href="https://dineshonjava.com/difference-between-hashmap-and/">Difference between HashMap and HashTable in Java</a></b></li>
<li><b><a href="https://dineshonjava.com/sorting-in-collection-framework/">Sorting</a></b></li>
<li><b><a href="https://dineshonjava.com/java-comparable-and-comparator/">Comparable interface</a></b></li>
</ol>
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