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Articles by George John
Page 33 of 79
Cancel the Timer Task in Java
In order to cancel the Timer Task in Java, we use the java.util.TimerTask.cancel() method. The cancel() method returns a boolean value, either true or false. The cancel() method is used to cancel the timer task.Declaration −The java.util.TimerTask.cancel() method is declared as follows −public boolean cancel()The cancel() methods returns true when the task is scheduled for one-time execution and has not executed until now and returns false when the task was scheduled for one-time execution and has been executed already.Let us see a program to illustrate the use of the java.util.TimerTask.cancel() method −Exampleimport java.util.*; class MyTask extends TimerTask { public ...
Read MoreAccess to the Group Database in Python
To access the UNIX group database, we should use the grp module. The shadow password database entries are like tuple like object.To use the grp module, we should import it using −import grpThe attributes of the grp database are −IndexAttribute & Description0gr_nameThe Name of the groups1gr_passwdThe Encrypted password for the group. (Generally empty)2gr_gidThe group id (Numeric)3gr_memA list of group usersIn the group object, the gid is an integer. The group name and the password are strings. The Member list is a list of strings.Some methods of this module are −Method grp.getgrgid(gid)This method will return group database entry from the given ...
Read MoreSubstitute tokens in a String in Java
To substitute tokens in a String in Java, we use the Message Format class. The Message Format class provides a means to produce concatenated messages which are not dependent on the language. The Message Format 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 ...
Read MoreJava program to print duplicates from a list of integers
In order to find duplicates we can utilize the property of Set in Java that in Java duplicates are not allowed when going to be added in a Set.Add method of set returns true for the adding value which is not added previously to it while it would return false in case the adding value is already present in the Set.For our agenda we would iterate out list or collection of integer and try to add each integer in a set of type integer.Now if integer gets added than this means that it is occurring for first time and not ...
Read MoreCompare two Strings lexicographically in Java programming
We can compare two strings lexicographically using following ways in Java.Using String.compareTo(String) method. It compares in case sensitive manner.Using String.compareToIgnoreCase(String) method. It compares in case insensitive manner.Using String.compareTo(Object) method. It compares in case sensitive manner.These methods returns the ascii difference of first odd characters of compared strings.Examplepublic class Tester { public static void main(String args[]) { String str = "Hello World"; String anotherString = "hello world"; Object objStr = str; System.out.println( str.compareTo(anotherString) ); System.out.println( str.compareToIgnoreCase(anotherString) ); System.out.println( str.compareTo(objStr.toString())); } }Output-32 0 0
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 MoreFibonacci of large number in java
Fibonacci numbers of Fibonacci series grows exponentially and can be very large for large numbers like 500 or 1000. To handle such number, long data type is not sufficient. BigInteger can handle large number easily. BigInteger is useful in scenarios where calculations results in data which is out of limit for available primitive data types. See the example below of getting Fibonacci number of 100 and 1000.Exampleimport java.math.BigInteger; public class Tester { public static void main(String args[]) { System.out.println("Fibonacci of 100: "); System.out.println(fibonacci(100)); System.out.println("Fibonacci of 1000: "); ...
Read MoreGet the list of all the public methods in Java
A list of all the public methods of a class or interface that is represented by an object are provided using the method java.lang.Class.getMethods(). The public methods include that are declared by the class or interface and also those that are inherited by the class or interface.Also, the getMethods() method returns a zero length array if the class or interface has no public methods or if a primitive type, array class or void is represented in the Class object.A program that demonstrates this is given as follows −Exampleimport java.lang.reflect.Method; public class Main { public static void main(String[] argv) throws ...
Read MoreWhat would getPackage() return for a class in unnamed package in Java?
The package for a class can be obtained using the java.lang.Class.getPackage() method with the help of the class loader of the class.The getPackage() method returns null for a class in unnamed package. A program that demonstrates this is given as follows −Exampleclass Class1 { public class Main { public static void main(String[] argv) throws Exception { Class c = Class1.class; System.out.println(c.getPackage()); } }OutputnullNow let us understand the above program.The getPackage() method is used to obtain the package for the class. However, the getPackage() method returns null for the class ...
Read MoreHow to swap or exchange objects in Java?
Java uses call by value while passing parameters to a function. To swap objects, we need to use their wrappers. See the example below −Examplepublic class Tester{ public static void main(String[] args) { A a = new A(); A b = new A(); a.value = 1; b.value = 2; //swap using objects swap(a, b); System.out.println(a.value +", " + b.value); Wrapper wA = new Wrapper(a); Wrapper wB = new Wrapper(b); ...
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