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Articles on Trending Technologies
Technical articles with clear explanations and examples
Do we need forward declarations in Java?
Forward declarations means the declaration of a method or variable prior to its implementation. Such declaration is necessary in C/C++ programming language in order to be able to use a variable or object before its implementation. In case, if we want to use a library code, then we need to create its header file and use it. But this is not a case in Java.Java allows using a variable, class prior to its declaration and implementation.Java allows using libraries code without any need of header files.Following example showcases the same. Here we have used a class object before its declaration.Examplepublic ...
Read MoreDifferent ways for Integer to String conversion in Java
Following are the different ways to convert an Integer to String in Java.Using Integer.toString(int) − Convert an int to String using static toString() method of Integer class.String b = Integer.toString(125);Using String.valueOf(int) − Convert an int to String using static valueOf() method of String class.String b = String.valueOf(125);Using new Integer(int).toString() − Convert an int to String using toString() method of Integer object.String b = new Integer(125).toString();Using DecimalFormat(pattern).format(int) − Convert an int to String using DecimalFormat.format() method.String b = new DecimalFormat("#").format(125);Using StringBuilder().toString() − Convert an int to String using StringBuilder.toString() method.String b = new StringBuilder().append(125).toString();Using StringBuffer().toString() − Convert an int to String ...
Read MoreDifference between ArrayList and CopyOnWriteArrayList in Java
Following are the notable differences between ArrayList and CopyOnWriteArrayList classes in Java. ArrayListCopyOnWriteArrayListSynchronizedArrayList is not synchronized.CopyOnWriteArrayList is synchronized.Thread SafeArrayList is not thread safe.CopyOnWriteArrayList is thread safe.Iterator typeArrayList iterator is fail-fast and ArrayList throws ConcurrentModificationException if concurrent modification happens during iteration.CopyOnWriteArrayList is fail-safe and it will never throw ConcurrentModificationException during iteration. The reason behind the it that CopyOnWriteArrayList creates a new arraylist every time it is modified.Remove OpearationArrayList iterator supports removal of element during iteration.CopyOnWriteArrayList.remove() method throws exception if elements are tried to be removed during iteration.PerformanceArrayList is faster.CopyOnWriteArrayList is slower than ArrayList.Since Java Version1.21.5Exampleimport java.util.Iterator; import java.util.concurrent.CopyOnWriteArrayList; public class Tester { ...
Read MoreDifference between HashMap and ConcurrentHashMap in Java
Following are the notable differences between HashMap and ConcurrentHashMap classes in Java. HashMapConcurrentHashMapSynchronizedHashMap is not synchronized.ConcurrentHashMap is synchronized.Thread SafeHashMap is not thread safe.ConcurrentHashMap is thread safe.Iterator typeHashMap iterator is fail-fast and ArrayList throws ConcurrentModificationException if concurrent modification happens during iteration.ConcurrentHashMap is fail-safe and it will never throw ConcurrentModificationException during iteration.Null valuesHashMap allows key and value to be null.ConcurrentHashMap does not allow null key/value. It will throw NullPointerException.PerformanceHashMap is faster.ConcurrentHashMap is slower than HashMap.Since Java Version1.21.5Exampleimport java.util.ArrayList; import java.util.Iterator; import java.util.List; import java.util.concurrent.CopyOnWriteArrayList; public class Tester { public static void main(String[] args) { ...
Read MoreHow to extract a group from a Java String that contains a Regex pattern
How to extract a group from a Java String that contains a Regex patternimport java.util.regex.Matcher; import java.util.regex.Pattern; public class RegexTest { public static void main(String[] args) { Pattern pattern = Pattern.compile("fun"); Matcher matcher = pattern.matcher("Java is fun"); // using Matcher find(), group(), start() and end() methods while (matcher.find()) { System.out.println("Found the text "" + matcher.group() + "" starting at " + matcher.start() + " index and ending at index ...
Read MoreHow can we get "MySQL server-side help"?
MySQL provides help command to get server-side help. The syntax of this command is as follows −mysql> help search_stringMySQL uses the argument of help command as the search string for accessing the contents of MySQL reference manual. The search will fail if there would be no match for the search string.For example − suppose I want to get server-side help regarding INTEGER data type then the command for the same would be as follows −mysql> help INTEGER Name: 'INTEGER' Description: INTEGER[(M)] [UNSIGNED] [ZEROFILL] This type is a synonym for INT. URL: http://dev.mysql.com/doc/refman/5.5/en/numeric-type-overview.html
Read MoreHow can we calculate the Date in MySQL using functions?
In MySQL, we can use the following functions to calculate the Date −CURDATE() Function − Basically it returns the current date of the computer.YEAR() Function − It returns the year of the specified date.MONTH() function − It returns the month of the specified date.DAY() Function − It returns the day of the specified date.RIGHT() Function − It returns the number of character as specified within the function from the given date. The part of the expression that compares the returns from RIGHT() function evaluates 1 or 0.To understand it, consider the data, as follows, from a table named ‘Collegedetail’ −mysql> ...
Read MoreHow can we use ORDER BY clause while calculating the Date?
It would be more convenient to find a record if we will use ORDER BY clause while calculating the date. To understand it, we have the data from table ‘Collegedetail’ as follows −mysql> Select * from Collegedetail; +------+---------+------------+ | ID | Country | Estb | +------+---------+------------+ | 111 | INDIA | 2010-05-01 | | 130 | INDIA | 1995-10-25 | | 139 | USA | 1994-09-25 | | 1539 | UK | 2001-07-23 | | 1545 ...
Read MoreDo we require any authentication for login into MySQL command line tool?
Yes, we require authentication for login into MySQL command line tool. For example, if we are trying to log in from windows command line then it will prompt for the password every time. The command for login is as follows −C:\Program Files\MySQL\bin>mysql -u root -p Enter password: *****
Read MoreHow can we find out the storage engine used for a particular table in MySQL?
The following MySQL statement can find out the storage engine used for ‘Student’ table in database named ‘tutorial’ −mysql> SELECT ENGINE FROM information_schema.TABLES -> WHERE TABLE_SCHEMA = 'tutorial' -> AND TABLE_NAME = 'Student'; +--------+ | ENGINE | +--------+ | MyISAM | +--------+ 1 row in set (0.13 sec)
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