Can you have duplicates in Hashtable?

Can you have duplicates in Hashtable?

Hashtable is synchronized and allows duplicate keys, but does not allow null keys or values. No, it will not allow duplicates.

How do I find duplicates in a HashMap?

How do you find duplicate characters in a string?

1. import java.util.HashMap;
2. import java.util.Map;
3. import java.util.Set;
4. public class DuplicateCharFinder {
5. public void findIt(String str) {
6. Map baseMap = new HashMap();
7. char[] charArray = str.toCharArray();

How do I find duplicate elements?

Duplicate elements can be found using two loops. The outer loop will iterate through the array from 0 to length of the array. The outer loop will select an element. The inner loop will be used to compare the selected element with the rest of the elements of the array.

How do I check if an array contains duplicate numbers?

function checkIfArrayIsUnique(myArray) { for (var i = 0; i < myArray. length; i++) { for (var j = 0; j < myArray. length; j++) { if (i != j) { if (myArray[i] == myArray[j]) { return true; // means there are duplicate values } } } } return false; // means there are no duplicate values. }

Can Hashtable have null values?

As specified in JDK documentation, Hashtable does not allow null keys or values. HashMap allows one null key and any number of null values.

Can Hashtable have duplicate keys in C#?

In hashtable, you can store elements of the same type and of the different types. The elements of hashtable that is a key/value pair are stored in DictionaryEntry, so you can also cast the key/value pairs to a DictionaryEntry. In Hashtable, key must be unique. Duplicate keys are not allowed.

How do you find duplicates in vectors?

Finding duplicates in a vector

1. Create a map of type to store the frequency count of each string in vector.
2. Iterate over all the elements in vector try to insert it in map as key with value as 1. If string already exists in map then increment its value by 1.

How do you find duplicates in string?

To find the duplicate character from the string, we count the occurrence of each character in the string. If count is greater than 1, it implies that a character has a duplicate entry in the string. In above example, the characters highlighted in green are duplicate characters.

How do you find duplicates in ArrayList?

Approach:

1. Get the ArrayList with duplicate values.
2. Create another ArrayList.
3. Traverse through the first arraylist and store the first appearance of each element into the second arraylist using contains() method.
4. The second ArrayList contains the elements with duplicates removed.

How do you check if there are duplicates in an array javaScript?

How to check if array contains duplicate values in javascript

1. Declare an empty object.
2. Iterate over the array using a for loop.
3. In every iteration, add a new entry in the object created in step 1 with the array element as key and with some fixed value.

How do you find duplicate values in an ArrayList?

Why is Hashtable synchronized?

Hashtable is synchronized. It ensures that no more than one thread can access the Hashtable at a given moment of time. The thread which works on Hashtable acquires a lock on it to make the other threads wait till its work gets completed. 2) HashMap allows one null key and any number of null values.