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Java Articles
Page 125 of 450
Add 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 ...
Read MoreDifference between HashTable and ConcurrentHashMap in Java
In this article, we will learn about the ConcurrentHashMap and HashTable in Java. First, we will know about ConcurrentHashMap, the syntax of ConcurrentHashMap, and an example after that will learn about HashTable, the syntax of HashTable, and an example. At the end, we will see a table showing the difference between ConcurrentHashMap and HashTable. What is ConcurrentHashMap in Java? ConcurrentHashMap is a class that was introduced in JDK 1.5. The ConcurrentHashMap is threadsafe as it allows multiple threads to read and write the data without locking the entire map. ConcurrentHashMap applies locks only at the bucket level, called a fragment, while ...
Read MoreHow to make a singleton enum in Java?
In Java, an enum is a special class used to represent a group of constants (that cannot be changed, like a final variable), such as Days: SUNDAY, MONDAY, TUESDAY, etc. Following is the syntax to create an Enum class in Java: enum ClassName { VALUE1, VALUE2, VALUE3, // ... VALUEN; } Where, enum is a reserved keyword in Java used to define an enum class, ClassName is the name of the enum, and VALUE1, VALUE2, VALUE3, ..., VALUEN are the ...
Read MoreHow to read the data from a properties file in Java?
Java supports file-handling; it provides various classes that provide various methods to read, write, update, and delete data from files in our local system. A properties file is a simple text file with a ".properties" extension that contains configuration data in the form of key-value pairs. It is mostly used in Java applications to manage settings such as database configuration, application messages, or environment variables. How to read Data from a Properties File in Java? To read data from the properties file, you can use the Properties class in Java. This is a subclass of the Hashtable class and it represents a persistent ...
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