SCJP : NavigableMap Mock Exam Practice Questions

Questions no -1 
What is the output for the below code ?

import java.util.NavigableMap;
import java.util.concurrent.ConcurrentSkipListMap;


public class Test {
	public static void main(String... args) {
        
		
		NavigableMap navMap = new 
        ConcurrentSkipListMap();
		
		navMap.put(4, "April");
		navMap.put(5, "May");
		navMap.put(6, "June");
		navMap.put(1, "January");
		navMap.put(2, "February");
		navMap.put(3, "March");

        navMap.pollFirstEntry();
        navMap.pollLastEntry();
        navMap.pollFirstEntry();
        System.out.println(navMap.size());


	     	      
	}
}




options
A)Compile error : No method  name like pollFirstEntry() or pollLastEntry()
B)3
C)6
D)4

Correct answer is : B

Explanations : 
pollFirstEntry() Removes and returns a key-value mapping associated with the least key in this map, or null if the map is empty.
pollLastEntry() Removes and returns a key-value mapping associated with the greatest key in this map, or null if the map is empty.

Questions no -2
What is the output for the below code ?

import java.util.NavigableMap;
import java.util.concurrent.ConcurrentSkipListMap;


public class Test {
	public static void main(String... args) {
        
		
		NavigableMap navMap = new 
        ConcurrentSkipListMap();
	
        System.out.print(navMap.lastEntry());


	     	      
	}
}



options
A)Compile error : No method  name like lastEntry()
B)null
C)NullPointerException
D)0

Correct answer is : B

Explanations : lastEntry() Returns a key-value mapping associated with the greatest key in this map, or null if the map is empty.

Questions no -3
What is the output for the below code ?

import java.util.NavigableMap;
import java.util.concurrent.ConcurrentSkipListMap;

public class Test {
	public static void main(String... args) {
        
		
		NavigableMapnavMap = new 
        ConcurrentSkipListMap();
		
		navMap.put(4, "April");
		navMap.put(5, "May");
		navMap.put(6, "June");
		navMap.put(1, "January");
		navMap.put(2, "February");
	

        System.out.print(navMap.ceilingKey(3));
        


	     	      
	}
}



options
A)Compile error : No method  name like ceilingKey()
B)null
C)NullPointerException
D)4

Correct answer is : D

Explanations : Returns the least key greater than or equal to the given key, or null if there is no such key. 
In the above case : 3 is not a key so return 4 (least key greater than or equal to the given key).

Questions no -4
What is the output for the below code ?

import java.util.NavigableMap;
import java.util.concurrent.ConcurrentSkipListMap;

public class Test {
	public static void main(String... args) {
        
		
		NavigableMapnavMap = new 
        ConcurrentSkipListMap();
		
		navMap.put(4, "April");
		navMap.put(5, "May");
		navMap.put(6, "June");
		navMap.put(1, "January");
		navMap.put(2, "February");
	

        System.out.print(navMap.floorKey(3));
        


	     	      
	}
}


options
A)Compile error : No method  name like floorKey()
B)null
C)NullPointerException
D)2

Correct answer is : D

Explanations : Returns the greatest key less than or equal to the given key, or null if there is no such key. 
In the above case : 3 is not a key so return 2 (greatest key less than or equal to the given key).