Article Categories
- All Categories
-
Data Structure
-
Networking
-
RDBMS
-
Operating System
-
Java
-
MS Excel
-
iOS
-
HTML
-
CSS
-
Android
-
Python
-
C Programming
-
C++
-
C#
-
MongoDB
-
MySQL
-
Javascript
-
PHP
-
Economics & Finance
Object Oriented Programming Articles
Page 450 of 589
Find free disk space using Java
java.io.File class provides following useful methods to figure out the free disk space available.Sr.No.Method & Description1public long getFreeSpace()Returns the number of unallocated bytes in the partition named by this abstract path name.2public long getTotalSpace()Returns the size of the partition named by this abstract pathname.3public long getUsableSpace()Returns the number of bytes available to this virtual machine on the partition named by this abstract pathname.Following example showcases the use of above methods.Example Finalimport java.io.File; import java.text.NumberFormat; public class Tester { public static void main(String[] args) { NumberFormat numberFormat = NumberFormat.getInstance(); numberFormat.setMaximumFractionDigits(2); ...
Read MoreFlexible nature of java.lang.object
The java.lang.Object class is the root of the class hierarchy. Every class has Object as a superclass. All objects, including arrays, implement the methods of this class.Class DeclarationFollowing is the declaration for java.lang.Object class −public class ObjectClass constructorsSr.No.Constructor & Description1Object()This is the Single Constructor.Class methodsSr.No.Method & Description1protected Object clone()This method creates and returns a copy of this object.2boolean equals(Object obj)This method indicates whether some other object is "equal to" this one.3protected void finalize()This method is called by the garbage collector on an object when garbage collection determines that there are no more references to the object.4Class getClass()This method returns the ...
Read MoreFloating point operators and associativity in Java
Following programs shows the float arithmetic can cause dubious result if integer values are used using float variables.Examplepublic class Tester { public static void main(String[] args) { float a = 500000000; float b = -500000000; float c = 1; float sumabc1 = a+(b+c); float sumabc2 =(a+b)+c; System.out.println("Floating Point Arithmetic"); System.out.println("a + ( b + c ) : " + sumabc1); System.out.println("(a + b) + c : " + sumabc2); ...
Read MoreWhy we should use whole string in Java regular expression
In Java regex matches() matches the input string against the whole string as it add a ^ and $ at the end of the input string.so it will not match the substring. So for matching substring, you should use find().Exampleimport java.util.regex.*; class PatternMatchingExample { public static void main(String args[]) { String content = "aabbcc"; String string = "aa"; Pattern p = Pattern.compile(string); Matcher m = p.matcher(content); System.out.println(" 'aa' Match:"+ m.matches()); System.out.println(" 'aa' Match:"+ m.find()); } }Output'aa' Match:false 'aa' Match:true
Read MoreFactory method to create Immutable Map in Java SE 9
With Java 9, new factory methods are added to Map interface to create immutable instances. These factory methods are convenience factory methods to create a collection in less verbose and in concise way.Old way to create collectionsExampleimport java.util.Collections; import java.util.HashMap; import java.util.Map; public class Tester { public static void main(String []args) { Map map = new HashMap(); map.put("A", "Apple"); map.put("B", "Boy"); map.put("C", "Cat"); Map readOnlyMap = Collections.unmodifiableMap(map); System.out.println(readOnlyMap); try { readOnlyMap.remove(0); ...
Read MoreExternalizable Interface in Java
Externalization is used whenever we need to customize serialization mechanism. If a class implements an Externalizable interface then, object serialization will be done using writeExternal() method. Whereas at receiver's end when an Externalizable object is a reconstructed instance will be created using no argument constructor and then the readExternal() method is called.If a class implements only Serializable interface object serialization will be done using ObjectoutputStream. At the receiver's end, the serializable object is reconstructed using ObjectInputStream.Below example showcases usage of Externalizable interface.Exampleimport java.io.Externalizable; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.IOException; import java.io.ObjectInput; import java.io.ObjectInputStream; import java.io.ObjectOutput; import java.io.ObjectOutputStream; public class ...
Read MoreDouble brace initialization in Java
Double braces can be used to create and initialize objects in a single Java expression. See the example below −Exampleimport java.util.ArrayList; import java.util.List; public class Tester{ public static void main(String args[]) { List list = new ArrayList(); list.add("A"); list.add("B"); list.add("C"); list.add("D"); list.add("E"); list.add("F"); System.out.println(list); List list1 = new ArrayList() { { add("A"); add("B");add("C"); add("D");add("E");add("F"); ...
Read MoreDo 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 More