- Java.util Package Classes
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- Java.util - ArrayDeque
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- Java.util - BitSet
- Java.util - Calendar
- Java.util - Collections
- Java.util - Currency
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- 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 TreeMap remove() Method
Description
The Java TreeMap remove(Object key) method is used to remove the mapping for this key from this TreeMap if present.
Declaration
Following is the declaration for java.util.TreeMap.remove() method.
public V remove(Object key)
Parameters
key − This is the key for which mapping should be removed.
Return Value
The method call returns the previous value associated with key, or null if there was no mapping for key.
Exception
ClassCastException − This exception is thrown if the specified key cannot be compared with the keys currently in the map.
NullPointerException − This exception is thrown if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys.
Removing a Key-Value Mapping from a TreeMap of Integer,Integer Pair Example
The following example shows the usage of Java TreeMap remove() method to remove a mapping based on key from the map. We've created a TreeMap object of Integer,Integer pairs. Then few entries are added using put() method, map is printed then using remove() we're removing a mapping for a key and map is printed again to see the effect of removing an entry.
package com.tutorialspoint; import java.util.TreeMap; public class TreeMapDemo { public static void main(String[] args) { // creating tree map TreeMap<Integer, Integer> treemap = new TreeMap<>(); // populating tree map treemap.put(2, 2); treemap.put(1, 1); treemap.put(3, 3); treemap.put(6, 6); treemap.put(5, 5); System.out.println("Value before modification: "+ treemap); // removing value at key 5 System.out.println("Removed value: "+treemap.remove(5)); System.out.println("Value after modification: "+ treemap); } }
Output
Let us compile and run the above program, this will produce the following result.
Value before modification: {1=1, 2=2, 3=3, 5=5, 6=6} Removed value: 5 Value after modification: {1=1, 2=2, 3=3, 6=6}
Removing a Key-Value Mapping from a TreeMap of Integer,String Pair Example
The following example shows the usage of Java TreeMap remove() method to remove a mapping based on key from the map. We've created a TreeMap object of Integer,String pairs. Then few entries are added using put() method, map is printed then using remove() we're removing a mapping for a key and map is printed again to see the effect of removing an entry.
package com.tutorialspoint; import java.util.TreeMap; public class TreeMapDemo { public static void main(String[] args) { // creating tree map TreeMap<Integer, String> treemap = new TreeMap<>(); // populating tree map treemap.put(2, "two"); treemap.put(1, "one"); treemap.put(3, "three"); treemap.put(6, "six"); treemap.put(5, "five"); System.out.println("Value before modification: "+ treemap); // removing value at key 5 System.out.println("Removed value: "+treemap.remove(5)); System.out.println("Value after modification: "+ treemap); } }
Output
Let us compile and run the above program, this will produce the following result.
Value before modification: {1=one, 2=two, 3=three, 5=five, 6=six} Removed value: five Value after modification: {1=one, 2=two, 3=three, 6=six}
Removing a Key-Value Mapping from a TreeMap of Integer,Object Pair Example
The following example shows the usage of Java TreeMap remove() method to remove a mapping based on key from the map. We've created a TreeMap object of Integer,Student pairs. Then few entries are added using put() method, map is printed then using remove() we're removing a mapping for a key and map is printed again to see the effect of removing an entry.
package com.tutorialspoint; import java.util.TreeMap; public class TreeMapDemo { public static void main(String[] args) { // creating tree map TreeMap<Integer, Student> treemap = new TreeMap<>(); // populating tree map treemap.put(2, new Student(2, "Robert")); treemap.put(1, new Student(1, "Julie")); treemap.put(3, new Student(3, "Adam")); treemap.put(6, new Student(6, "Julia")); treemap.put(5, new Student(5, "Tom")); System.out.println("Value before modification: "+ treemap); // removing value at key 5 System.out.println("Removed value: "+treemap.remove(5)); System.out.println("Value after modification: "+ treemap); } } class 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) { if(obj == null) return false; Student s = (Student)obj; return this.rollNo == s.rollNo && this.name.equalsIgnoreCase(s.name); } }
Output
Let us compile and run the above program, this will produce the following result.
Value before modification: {1=[ 1, Julie ], 2=[ 2, Robert ], 3=[ 3, Adam ], 5=[ 5, Tom ], 6=[ 6, Julia ]} Removed value: [ 5, Tom ] Value after modification: {1=[ 1, Julie ], 2=[ 2, Robert ], 3=[ 3, Adam ], 6=[ 6, Julia ]}
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