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Articles on Trending Technologies
Technical articles with clear explanations and examples
How many types of anonymous inner classes are defined in Java?
An anonymous inner class is an inner class which is declared without any class name at all. In other words, a nameless inner class is called an anonymous inner class. Since it does not have a name, it cannot have a constructor because we know that a constructor name is the same as the class name.We can define an anonymous inner class and create its object using the new operator at the same time in one step.Syntaxnew(argument-list){ // Anonymous class body }Types of Anonymous Inner Class in JavaAnonymous inner class that extends a classAnonymous inner class that implements an interfaceAnonymous inner ...
Read MoreJava Program to get minimum value with Comparator
First, declare an integer array and add some elements −Integer arr[] = { 40, 20, 30, 10, 90, 60, 700 };Now, convert the above array to List −List list = Arrays.asList(arr);Now, use Comparator and the reverseOrder() method. Using max() will eventually give you the maximum value, but with reverseOrder() it reverses the result −Comparator comp = Collections.reverseOrder(); System.out.println("Minimum element = "+Collections.max(list, comp));Exampleimport java.util.Arrays; import java.util.Collections; import java.util.Comparator; import java.util.List; public class Demo { @SuppressWarnings("unchecked") public static void main(String args[]) { Integer arr[] = { 40, 20, 30, 10, 90, 60, 700 }; ...
Read MoreWhat is AbstractList Class in Java?
The AbstractList class provides an implementation of the List interface.For an unmodifiable listProgrammer needs to extend this class and provide implementations for the get(int) and size() methods.For a modifiable listProgrammer must override the set(int, E) method. If the list is variable-size the programmer must override the add(int, E) and remove(int) methods.The following is the syntax:public abstract class AbstractList extends AbstractCollection implements ListTo work with the AbstractList class, import the following package:import java.util.AbstractList;The following is an example to implement AbstractList class:Exampleimport java.util.LinkedList; import java.util.AbstractList; public class Demo { public static void main(String[] args) { AbstractList myList = ...
Read MoreJava Program to convert java.util.Date to LocalDate
At first set the date with java.util.Date −java.util.Date date = new Date();Now, convert the date to LocalDate −Instant instant = Instant.ofEpochMilli(date.getTime()); System.out.println("LocalDate = "+LocalDateTime.ofInstant(instant, ZoneId.systemDefault()).toLocalDate());Exampleimport java.time.Instant; import java.time.LocalDateTime; import java.time.ZoneId; import java.util.Date; public class Demo { public static void main(String[] args) { java.util.Date date = new Date(); System.out.println("Date = "+date); Instant instant = Instant.ofEpochMilli(date.getTime()); System.out.println("LocalDate = "+LocalDateTime.ofInstant(instant, ZoneId.systemDefault()).toLocalDate()); } }OutputDate = Thu Apr 18 23:51:06 IST 2019 LocalDate = 2019-04-18
Read MoreHow to add elements to AbstractList class in Java?
To add elements to AbstractList class, the add() method is provided by the AbstractList class. The elemnt gets appended at the end of the list.The syntax is as follows:public boolean add(E ele)Here, the parameter ele is an element to be appended to this listTo work with the AbstractList class, import the following package:import java.util.AbstractList;The following is an example to add elements to AbstractlList class in Java:Exampleimport java.util.LinkedList; import java.util.AbstractList; public class Demo { public static void main(String[] args) { AbstractList myList = new LinkedList(); myList.add(50); myList.add(100); myList.add(150); ...
Read MoreWhat is the difference between String, StringBuffer and StringBuilder classes in Java explain briefly?
The String class of the java.lang package represents character strings. All string literals in Java programs, such as "abc", are implemented as instances of this class. Strings are constant, their values cannot be changed after they are created.The StringBuffer and StringBuilder classes are used when there is a necessity to make a lot of modifications to Strings of characters.Unlike Strings, objects of type StringBuffer and String builder can be modified over and over again without leaving behind a lot of new unused objects.The StringBuilder class was introduced as of Java 5 and the main difference between the StringBuffer and StringBuilder ...
Read MoreWhat is an OutOfMemoryError and steps to find the root cause of OOM in Java?
The OutOfMemoryError is thrown by JVM, when JVM does not have enough available memory, to allocate. OutOfMemoryError falls into the Error category in Exception class hierarchy.To generate OutOfMemoryErrorWe will allocate a large chunk of memory, which will exhaust heap memory storage.We will keep on allocating the memory and point will reach, when JVM will not have enough memory to allocate, then OutOfMemoryError will be thrown.Once we will catch the OutOfMemory error, we can log the error.Examplepublic class OutOfMemoryErrorDemo { public static void main(String[] args) throws Exception { int dummyArraySize = 15; System.out.println("Max JVM memory: " + Runtime.getRuntime().maxMemory()); ...
Read MoreHow can I swap two strings without using a third variable in Java?
To swap the contents of two strings (say s1 and s2) without the third.First of all concatenate the given two strings using the concatenation operator “+” and store in s1 (first string).s1 = s1+s2;The substring method of the String class is used to this method has two variants and returns a new string that is a substring of this string. The substring begins with the character at the specified index and extends to the end of this string or up to endIndex – 1, if the second argument is given.Now using the substring() method of the String class store the ...
Read MoreConvert from String to long in Java
To convert String to long, the following are the two methods.Method 1The following is an example wherein we use parseLong() method.Examplepublic class Demo { public static void main(String[] args) { String myStr = "5"; Long myLong = Long.parseLong(myStr); System.out.println("Long: "+myLong); } }OutputLong: 5Method 2The following is an example wherein we have used valueOf() and longValue() method to convert String to long.Examplepublic class Demo { public static void main(String[] args) { String myStr = "20"; long res = Long.valueOf(myStr).longValue(); System.out.println("Long: "+res); } }OutputLong: 20
Read MoreGenerate Random Float type number in Java
In order to generate Random float type numbers in Java, we use the nextFloat() method of the java.util.Random class. This returns the next random float value between 0.0 (inclusive) and 1.0 (exclusive) from the random generator sequence.Declaration −The java.util.Random.nextFloat() method is declared as follows −public float nextFloat()Let us see a program to generate random float type numbers in Java.Exampleimport java.util.Random; public class Example { public static void main(String[] args) { Random rd = new Random(); // creating Random object System.out.println(rd.nextFloat()); // displaying a random float value between 0.0 and 1.0 } }Output0.7739767Note ...
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