TreeSet : floor

E floor(E e)

return the greatest element less than or equal to e,or null if there is no such element

import java.util.*;

class TreeSetFloor{
 public static void main(String args[]){
  TreeSet<Integer> mySet = new TreeSet<> ();
  
  for(int i=20; i >0; i-=2)
   mySet.add(i);
   
  System.out.println("Elements in mySet are");
  System.out.println(mySet+"\n");
  
  for(int i =1; i <= 25; i+=2){
   System.out.print("Floor Element of " + i +" is ");
   System.out.println(mySet.floor(i));
  }   
 }
}

Output

Elements in mySet are
[2, 4, 6, 8, 10, 12, 14, 16, 18, 20]

Floor Element of 1 is null
Floor Element of 3 is 2
Floor Element of 5 is 4
Floor Element of 7 is 6
Floor Element of 9 is 8
Floor Element of 11 is 10
Floor Element of 13 is 12
Floor Element of 15 is 14
Floor Element of 17 is 16
Floor Element of 19 is 18
Floor Element of 21 is 20
Floor Element of 23 is 20
Floor Element of 25 is 20

1. throws NullPointerException if the specified element is null 

import java.util.*;

class TreeSetFloorNullPointer{
 public static void main(String args[]){
  TreeSet<Integer> mySet = new TreeSet<> ();
  
  for(int i=20; i >0; i-=2)
   mySet.add(i);
   
  System.out.println("Elements in mySet are");
  System.out.println(mySet+"\n");

  System.out.println("Floor Element Of null is");
  mySet.floor(null);
 }
}

Output

Elements in mySet are
[2, 4, 6, 8, 10, 12, 14, 16, 18, 20]

Floor Element Of null is
Exception in thread "main" java.lang.NullPointerException
        at java.util.TreeMap.compare(TreeMap.java:1188)
        at java.util.TreeMap.getFloorEntry(TreeMap.java:422)
        at java.util.TreeMap.floorKey(TreeMap.java:725)
        at java.util.TreeSet.floor(TreeSet.java:425)
        at TreeSetFloorNullPointer.main(TreeSetFloorNullPointer.java:14)

2. throws ClassCastException if the specified element cannot be compared with the elements currently in the set

 

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