- Java.util Package Classes
- Java.util - Home
- Java.util - ArrayDeque
- Java.util - ArrayList
- Java.util - Arrays
- Java.util - BitSet
- Java.util - Calendar
- Java.util - Collections
- Java.util - Currency
- Java.util - Date
- Java.util - Dictionary
- Java.util - EnumMap
- Java.util - EnumSet
- Java.util - Formatter
- Java.util - GregorianCalendar
- Java.util - HashMap
- Java.util - HashSet
- Java.util - Hashtable
- Java.util - IdentityHashMap
- Java.util - LinkedHashMap
- Java.util - LinkedHashSet
- Java.util - LinkedList
- Java.util - ListResourceBundle
- Java.util - Locale
- Java.util - Observable
- Java.util - PriorityQueue
- Java.util - Properties
- Java.util - PropertyPermission
- Java.util - PropertyResourceBundle
- Java.util - Random
- Java.util - ResourceBundle
- Java.util - ResourceBundle.Control
- Java.util - Scanner
- Java.util - ServiceLoader
- Java.util - SimpleTimeZone
- Java.util - Stack
- Java.util - StringTokenizer
- Java.util - Timer
- Java.util - TimerTask
- Java.util - TimeZone
- Java.util - TreeMap
- Java.util - TreeSet
- Java.util - UUID
- Java.util - Vector
- Java.util - WeakHashMap
- Java.util Package Extras
- Java.util - Interfaces
- Java.util - Exceptions
- Java.util - Enumerations
- Java.util Useful Resources
- Java.util - Useful Resources
- Java.util - Discussion
Java TreeSet contains() Method
Description
The Java TreeSet contains(Object o) method is used to return true if and only if this set contains the specified element.
Declaration
Following is the declaration for java.util.TreeSet.contains() method.
public boolean contains(Object o)
Parameters
o − This is the object to be checked for containment in this set.
Return Value
The method call returns true if this set contains the specified element.
Exception
ClassCastException − This is thrown if the specified element cannot be compared with the elements currently exists in the set.
NullPointerException − This is thrown if the specified element is null and this set uses natural ordering, or its comparator does not permit null elements.
Checking an Element's Presence in a TreeSet of Integer Example
The following example shows the usage of Java TreeSet contains() method to check if an element is present in the treeset. We've created a TreeSet object of Integer. Then few entries are added using add() method and an element is checked in the set and result is printed.
package com.tutorialspoint; import java.util.TreeSet; public class TreeSetDemo { public static void main(String[] args) { // creating a TreeSet TreeSet <Integer>treeset = new TreeSet<>(); // adding in the tree set treeset.add(12); treeset.add(13); treeset.add(14); treeset.add(15); // check existence of 15 System.out.println("Checking existence of 15 "); System.out.println("Is 15 there in the set: "+treeset.contains(15)); } }
Output
Let us compile and run the above program, this will produce the following result.
Checking existence of 15 Is 15 there in the set: true
Checking an Element's Presence in a TreeSet of String Example
The following example shows the usage of Java TreeSet contains() method to check if an element is present in the treeset. We've created a TreeSet object of String. Then few entries are added using add() method and an element is checked in the set and result is printed.
package com.tutorialspoint; import java.util.TreeSet; public class TreeSetDemo { public static void main(String[] args) { // creating a TreeSet TreeSet <String>treeset = new TreeSet<>(); // adding in the tree set treeset.add("12"); treeset.add("13"); treeset.add("14"); treeset.add("15"); // check existence of "15" System.out.println("Checking existence of 15 "); System.out.println("Is 15 there in the set: "+treeset.contains("15")); } }
Output
Let us compile and run the above program, this will produce the following result.
Checking existence of 15 Is 15 there in the set: true
Checking an Element's Presence in a TreeSet of Object Example
The following example shows the usage of Java TreeSet contains() method to check if an element is present in the treeset. We've created a TreeSet object of Student objects. Then few entries are added using add() method and an element is checked in the set and result is printed.
package com.tutorialspoint; import java.util.TreeSet; public class TreeSetDemo { public static void main(String[] args) { // creating a TreeSet TreeSet <Student>treeset = new TreeSet<>(); // adding in the tree set treeset.add(new Student(1, "Robert")); treeset.add(new Student(2, "Julie")); treeset.add(new Student(3, "Adam")); treeset.add(new Student(4, "Julia")); // check existence of "Adam" System.out.println("Checking existence of 15 "); System.out.println("Is Adam there in the set: "+treeset.contains(new Student(3, "Adam"))); } } class Student implements Comparable<Student> { int rollNo; String name; Student(int rollNo, String name){ this.rollNo = rollNo; this.name = name; } @Override public String toString() { return "[ " + this.rollNo + ", " + this.name + " ]"; } @Override public boolean equals(Object obj) { Student s = (Student)obj; return this.rollNo == s.rollNo && this.name.equalsIgnoreCase(s.name); } @Override public int compareTo(Student student) { return this.rollNo - student.rollNo; } }
Output
Let us compile and run the above program, this will produce the following result.
Checking existence of 15 Is Adam there in the set: true