TASK: Which of the following statements about the Java HashMap are true? (Select all that apply)...
TASK: Which of the following statements about the Java HashMap are true? (Select all that apply)
Select all correct options from the list
If you try to store a key that’s already in a HashMap, the previous value associated with the key will be overwritten
You cannot store duplicate values in a HashMap
A HashMap can only use non-primitive types as keys
A HashMap cannot have null as a key
A HashMap can have multiple null keys
A HashMap can have multiple null values
Homework Answers
Please find your answers below.
Statement: If you try to store a key that’s already in a HashMap, the previous value associated with the key will be overwritten
Answer: True. HashMap cannot have duplicate keys, so if we try to add a duplicate key to a hash map, then the previously stored value will be overwritten by the new value.
Statement: You cannot store duplicate values in a HashMap
Answer: False, values can have duplicates in HashMap, but not keys. For example, if map is a HashMap with key=Integer, Value=String, then the statements map.put(1,”Java”); map.put(2,”Java”); will create two different entries in the map with value=”Java”. But if the key was duplicated, the old value will be replaced by new one as mentioned earlier.
Statement: A HashMap can only use non-primitive types as keys
Answer: True, primitive types like int, float, double, char etc cannot be keys in a HashMap, but we can use non primitive types like Integer, Float, Double etc. Those primitive type values will be type casted automatically to corresponding non primitive types if we pass a primitive type as key while adding or updating an entry in hashmap.
Statement: A HashMap cannot have null as a key
Answer: False, A HashMap can have entries with key=null. Though it is not possible to create a HashMap with key type=null, we can add an entry with key = null into a hashmap of any type.
Statement: A HashMap can have multiple null keys
Answer: False, just like any other keys, a HashMap cannot have duplicate null values as keys. If there is already a null value as key, the value will be overwritten by the new value just as we specified earlier.
Statement: A HashMap can have multiple null values
Answer: True, we can add as many null values as values for unique keys into a hash map.
Take all the statements with answer equals True, and you got your answers. Let me know if you have any doubts or if you need anything to change. If you are satisfied with the solution, please rate the answer. Thanks
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