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Articles on Trending Technologies
Technical articles with clear explanations and examples
Convert an ArrayList to an Array with zero length Array in Java
An ArrayList can be converted into an Array using the java.util.ArrayList.toArray() method. This method takes a single parameter i.e. the array of the required type into which the ArrayList elements are stored and it returns an Array that contains all the elements of the ArrayList in the correct order.A program that demonstrates this is given as follows −Exampleimport java.util.ArrayList; import java.util.List; public class Demo { public static void main(String[] args) { List aList = new ArrayList(); aList.add("James"); aList.add("Harry"); aList.add("Susan"); aList.add("Emma"); aList.add("Peter"); ...
Read MoreCount the Number of matching characters in a pair of Java string
In order to find the count of matching characters in two Java strings the approach is to first create character arrays of both the strings which make comparison simple.After this put each unique character into a Hash map.Compare each character of other string with created hash map whether it is present or not in case if present than put that character into other hash map this is to prevent duplicates.In last get the size of this new created target hash map which is equal to the count of number of matching characters in two given strings.Exampleimport java.util.HashMap; public class MatchingCharacters ...
Read MoreBoolean Literals in Java
The Boolean literals have two values i.e. True and False.The following is an example to display Boolean Literals.Examplepublic class Demo { public static void main(String[] args) { System.out.println("Boolean Literals"); boolean one = true; System.out.println(one); one = false; System.out.println(one); } }OutputBoolean Literals true falseIn the above program, we have declared a boolean value and assigned the boolean literal “true”.boolean one = true;In the same way, we have added another boolean literal “false”.one = false;Both of the above values are displayed, which are the boolean literals.
Read MoreGet current time information in Java
Import the following package for to work with Calendar class in Java, import java.util.Calendar;Create a calendar class now.Calendar cal = Calendar.getInstance();To display entire time information, use the following fields.cal.get(Calendar.HOUR_OF_DAY) cal.get(Calendar.HOUR) cal.get(Calendar.MINUTE) cal.get(Calendar.SECOND) cal.get(Calendar.MILLISECOND)The following is the final example.Exampleimport java.util.Calendar; public class Demo { public static void main(String[] args) { Calendar cal = Calendar.getInstance(); // current date and time System.out.println(cal.getTime().toString()); // time information System.out.println("Hour (24 hour format) : " + cal.get(Calendar.HOUR_OF_DAY)); System.out.println("Hour (12 hour format) : " + cal.get(Calendar.HOUR)); ...
Read MoreValidate city and state with Java Regular Expressions
In order to match the city and state using regular expression, we use the matches method in Java. The java.lang.String.matches() method returns a boolean value which depends on the matching of the String with the regular expression.Declaration − The java.lang.String.matches() method is declared as follows −Examplepublic class Example { public static void main( String[] args ) { System.out.println(city("Mumbai")); System.out.println(state("Goa")); } // validating the city public static boolean city( String c ) { return c.matches( "([a - zA - Z] + |[a - zA - Z] + \s[a ...
Read MoreValidate the ZIP code with Java Regular expressions
In order to match the ZIP code using regular expression, we use the matches method in Java. The java.lang.String.matches() method returns a boolean value which depends on the matching of the String with the regular expression.Declaration − The java.lang.String.matches() method is declared as follows −public boolean matches(String regex)Let us see a program which validates the ZIP code with Java Regular Expressions −Examplepublic class Example { public static void main( String[] args ) { System.out.println(zipIndia("400709")); System.out.println(zipUS("10060")); } // validate zip public static boolean zipIndia( String z ) { ...
Read MoreDifference between TreeMap, HashMap and LinkedHashMap in Java programming
HashMap, TreeMap and LinkedHashMap all implements java.util.Map interface and following are their characteristics.HashMapHashMap has complexity of O(1) for insertion and lookup.HashMap allows one null key and multiple null values.HashMap does not maintain any order.TreeMapTreeMap has complexity of O(logN) for insertion and lookup.TreeMap does not allow null key but allow multiple null values.TreeMap maintains order. It stores keys in sorted and ascending order.LinkedHashMapLinkedHashMap has complexity of O(1) for insertion and lookup.LinkedHashMap allows one null key and multiple null values.LinkedHashMap maintains order in which key-value pairs are inserted.Exampleimport java.util.HashMap; import java.util.Hashtable; import java.util.LinkedHashMap; import java.util.Map; import java.util.TreeMap; public class Tester { ...
Read MoreFormat floating point with Java MessageFormat
To format message with floating point fillers in Java, we use the MessageFormat class. The MessageFormat class gives us a way to produce concatenated messages which are not dependent on the language. The MessageFormat class extends the Serializable and Cloneable interfaces.Declaration −The java.text.MessageFormat class is declared as follows −public class MessageFormat extends FormatThe MessageFormat.format(pattern, params) method formats the message and fills in the missing parts using the objects in the params array matching up the argument numbers and the array indices.The format method has two arguments, a pattern and an array of arguments. The pattern contains placeholder in {} curly ...
Read MoreDifference between x++ and x= x+1 in Java programming
x++ automatically handles the type casting where as x= x + 1 needs typecasting in case of x is not an int variable. See the example below.Examplepublic class Tester { public static void main(String args[]) { byte b = 2; //Type casting is required //as 1 is int and b is byte variable b = (byte) (b + 1); System.out.println(b); byte b1 = 2; //Implcit type casting by the compiler b1++; System.out.println(b1); } }Output3 3
Read MoreConvert Java String Object to Boolean Object
A string object can be created in Java using the string literal.String myStr = “Amit”;Another way to create a string object is using the new keyword.String myStr = new String("Hello!");We have used the first method to create a string object.String str = "true";Now, use the valueOf() method to convert String Object to Boolean Object. We have used this method on Boolean object.Boolean bool = Boolean.valueOf(str);Let us now see the complete example to show how to convert String Object to Boolean Object.Examplepublic class Demo { public static void main(String[] args) { String str = "true"; ...
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