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HashMap is a popular class of Collections framework which is used to store key value pair. There are 2 ways to iterate over the hashmap and access its keys and values. Let us look at these ways: Using entrySet() method entrySet() method returns a Set of Map.Entry<K,V> type, where K is key and V is … Read more
We are not allowed to enter duplicate keys in HashMap, but we can enter duplicate values in it. Please note here that, if we enter duplicate keys no error will be thrown but the latest key-value pair entered will replace the old key-value pair. Let us see with an example: In the above code we … Read more
HashMap is one of the most used collections in Java. It is used to store key value pair. The size of HashMap increases as more key value pairs are added. Let us look at sample declaration of HashMap: HashMap<Integer,String> dummy = new HashMap<Integer,String>(); In above sample the key stored will be of type Integer and … Read more
ArrayList is a dynamic array which means the size of arraylist increases as the elements are added. The number by which the size is increased is known as Growth Factor. In ArrayList the Growth factor is 1.5, which means everytime the size of list is to be increased it is increased by 1.5. Example:- If … Read more
Arraylist is a dynamic array whose size increases as we add more elements to it. When an ArrayList is created without specifying its size then the size of Arraylist initially is zero. But when we add the first element to the list then size of ArrayList is increased to 10. This can be shown by … Read more
ArrayList is one of the most used Collections in java. It is a dynamic array which means its size can increase automatically as more elements are added to it. Let us see how to create an arraylist: ArrayList<Integer> arrList = new ArrayList<Integer>(); We need to give the object type within angle brackets which tells the … Read more
There are many times when we may need to know the class name of the object being used. Example :- If we are iterating a list of different objects and we need to know the class name of the objects. To know the class name we use objectName.getClass().getName() Let us look at an example code: … Read more
Parsing in java is the way of conversion of one type of data to another type of data. In java the most common parsing conversions are : Parsing string to integer. Parsing string to long type. Parsing string to double type. Let us look at a code to look at above parsing ways : Output … Read more
NumberFormatException occurs in Java when we are trying to convert string into some numeric type but string is not in the correct format. It usually occurs when we parse string to integer, double, long etc datatypes but string is not present in correct format. Let us see an example code : Output Since ‘123a’ cannot … Read more
In Java we have 4 type of variables :- Local Variable Instance Variable Class variable Reference variable Java developers often get confused while using these terms, let us understand the difference between them in detail : Local Variable Local variables are those which are defined inside a block, method or constructor. These variables get destroyed … Read more