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Java Articles
Page 128 of 450
Check if a particular key exists in Java LinkedHashMap
LinkedHashMap is a data structure in Java that is part of the Java Collections Framework. It is very similar to HashMap.It stores key-value pairs, where each key is unique, and it allows null values, but allows only one null key. The main difference is that the LinkedHashMap returns the elements in the order they were inserted. This is because it maintains a linked list with entries in the map, which helps it to retain the insertion order of the elements. Our task is to check if a particular key exists in a LinkedHashMap in Java. Scenario 1 Following is a ...
Read MoreHow can we Implement a Stack using Queue in Java?
This article will discuss how to implement a Stack using a Queue in Java. Stack in Java In Java, a Stack is a subclass (child class) of the Vector class, and it represents a LIFO stack of objects, which stands for Last-in-First-Out. The last element added at the top of the stack (In) can be the first element to be removed (Out) from the stack. The following diagram will give you a clear idea about the Stack: Queue in Java In Java, the Queue class extends the Collection interface, and it supports the insert and remove operations using a FIFO, ...
Read MoreHow can we Implement a Queue using Stack in Java?
This article will discuss how to implement a Queue using a Stack in Java. It will briefly introduce the Queues and Stacks, and provide a suitable example that shows their implementation. Queues in Java In Java, the Queue class extends the Collection interface, and it supports the insert and remove operations using a FIFO (First-in-First-Out). The last element added to the end of the queue can become the first element to be removed from the queue. The following diagram will give you a better understanding of the Queue: Stacks in Java In Java, a Stack is a subclass (child class) ...
Read MoreAdd all the elements from a collection to the HashSet in Java
HashSet in Java implements the Set interface, which belongs to the Java Collections Framework and is a part of the java.util package. It stores unique elements, which means we cannot store any duplicate (appearing more than once) values in a HashSet. The given task is to add all the elements of another collection to a HashSet object in Java. For example, if we have a collection ArrayList with elements [1, 3, 4, 5, 5]. Our task is to add all these elements to a HashSet, maybe to remove duplicates from the list, or for any other reason. Adding Elements from ...
Read MoreAdd months to current date using Calendar.add() method in Java
The given task is to add months to a date (object) using the add() method of the Calendar class. For example, if we need to add 5 months to the date: 26-06-2025, the new date would be 26-11-2025. Calendar.add() method in Java The calender.add() method in Java is used to add a specified amount of time to any field of the Calendar. Using this method, we can add months, years, days, etc. This method accepts two parameters: the first one is the field we want to add to, and the second one is the amount we want to ...
Read MoreAdd elements to HashMap in Java
HashMap is a part of the Java Collections Framework, it is available in java.util package. It implements the Map interface, and it is used for storing two values at a time: a key and a value. The HashMap key is used to access the associated value. A Java HashMap is similar to a dictionary, where we have a word (key) and its meaning is considered as a value. In this article, we will learn how to add elements to a HashMap in Java Programming. The following are the ways to add elements to a HashMap in Java: Using ...
Read MoreHow to check multiple regex patterns against an input? Using Java.
In Java, the strings that are used to find the pattern are known as regular expressions. In this article, we will learn to check multiple regex patterns against an input, and it can be done by using 2 approaches. Using Metacharacter Using the List object Using Metacharacter The meta character "|" in Java regular expressions allows you to match more than one regular expression. For example, if you need to match a particular input text with more than one expression, you need to separate them using the following: exp1|exp2|exp3 Example ...
Read MoreCount the number of columns in a MySQL table with Java
In this article, we will learn how to count the number of columns in a MySQL table using JDBC. We will be using the ResultSetMetaData to get details of the table by using simple examples. What is ResultSetMetaData? The ResultSetMetaData is an interface that is present in the java.sql package. Using ResultSetMetaData, we can get information about the table, for example, what are the column names of each and every table, and how many columns are there?. To create the object for ResultSet: ResultSet rs=st.executeQuery("Select * from Student"); The executeQuery method writes the records, which are then stored in the ...
Read MoreAdd a value to Pair Tuple in Java
By default, Java does not have built-in tuple support; to use the tuple, we use the third-party library called Javatuples. Using this library, you can create a tuple of different sizes, starting from a single-element tuple, which is the Unit class, up to a ten-element tuple (Decade class). The following is the list of JavaTuples library classes: Unit: 1 element tuple Pair: 2 element tuple Triplet: 3 element tuple Quartet: 4 element tuple Quintet: 5 element tuple ...
Read MoreAdd a value in Ennead Tuple in Java
By default, Java does not have built-in tuple support; to use the tuple, we use the third-party library called Javatuples. Using this library, you can create a tuple of different sizes, starting from a single-element tuple, which is the Unit class, up to a ten-element tuple (Decade class). The following is the list of JavaTuples library classes: Unit: 1 element tuple. Pair: 2 element tuple. Triplet: 3 element tuple Quartet: 4 element tuple Quintet: 5 element tuple ...
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