What is the best way to iterate list in Java?
- Using loops (Naive Approach) For loop. For-each loop. While loop.
- Using Iterator.
- Using List iterator.
- Using lambda expression.
- Using stream.forEach()
How many ways we can iterate collection in Java?
There are three common ways to iterate through a Collection in Java using either while(), for() or for-each(). While each technique will produce more or less the same results, the for-each construct is the most elegant and easy to read and write.
What are the different ways to iterate over an array in Java?
There are multiple ways to loop over an array in Java, like you can use a for loop, an enhanced for loop, a while loop, or a do-while loop.
What are the three ways to iterate over a HashMap?
Three ways to iterate a Hashmap
- Using a for loop to iterate through a HashMap.
- Using a forEach to iterate through a HashMap.
- Using an iterator to iterate through a HashMap.
How do you iterate through a list of objects?
How to iterate over a Java list?
- Obtain an iterator to the start of the collection by calling the collection’s iterator() method.
- Set up a loop that makes a call to hasNext(). Have the loop iterate as long as hasNext() returns true.
- Within the loop, obtain each element by calling next().
How do I compare two lists in Java?
Java provides a method for comparing two Array List. The ArrayList. equals() is the method used for comparing two Array List. It compares the Array lists as, both Array lists should have the same size, and all corresponding pairs of elements in the two Array lists are equal.
What is the difference between List and map?
Map doesn’t allow duplicate keys while it allows duplicate values. 2) Null values: List allows any number of null values. Set allows single null value at most. Map can have single null key at most and any number of null values.
Can we iterate HashMap?
There is a numerous number of ways to iterate over HashMap of which 5 are listed as below: Iterate through a HashMap EntrySet using Iterators. Iterate through HashMap KeySet using Iterator. Iterate HashMap using for-each loop.
How do you sort an ArrayList?
To sort the ArrayList, you need to simply call the Collections. sort() method passing the ArrayList object populated with country names. This method will sort the elements (country names) of the ArrayList using natural ordering (alphabetically in ascending order).
What is a for each loop in Java?
Java 5 introduced an for-each loop, which is called a enhanced for each loop. It is used to iterate over elements of an array and the collection. for-each loop is a shortcut version of for-loop which skips the need to get the iterator and loop over iterator using it’s hasNext() and next() method.
How do you iterate in Java?
Java – How to Use Iterator?
- Obtain an iterator to the start of the collection by calling the collection’s iterator( ) method.
- Set up a loop that makes a call to hasNext( ). Have the loop iterate as long as hasNext( ) returns true.
- Within the loop, obtain each element by calling next( ).
What is the difference between HashMap and Hashtable?
HashMap is non-synchronized. It is not thread-safe and can’t be shared between many threads without proper synchronization code whereas Hashtable is synchronized. … HashMap allows one null key and multiple null values whereas Hashtable doesn’t allow any null key or value.
How do I sort a HashMap?
Steps to sort HashMap by values
- Get all entries by calling entrySet() method of Map.
- Create a custom Comparator to sort entries based upon values.
- Convert entry set to list.
- Sort entry list by using Collections. sort() method by passing your value comparator.
- Create a LinkedHashMap by adding entries in sorted order.
How many ways we can iterate HashMap?
There are generally five ways of iterating over a Map in Java.