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Object Oriented Programming Articles
Page 580 of 589
Atomic variables in Java
Yes, from Java 8 onwards, java.util.concurrent.atomic package contains classes which support atomic operations on single variables preventing race conditions or do not face synchronization issues. All classes in the atomic package have get/set methods. Each set method has a happens-before relationship with any subsequent get() method call on the same variable. import java.util.concurrent.atomic.AtomicInteger; class AtomicCounter { private AtomicInteger counter = new AtomicInteger(0); public void increment() { counter.incrementAndGet(); } public void decrement() { counter.decrementAndGet(); } public int value() { return counter.get(); } }
Read MoreDifferences between & and && operators in Java.
& is a bitwise operator and compares each operand bitwise.It is a binary AND Operator and copies a bit to the result if it exists in both operands.Assume integer variable A holds 60 and variable B holds 13 then (A & B) will give 12 which is 0000 1100.Whereas && is a logical AND operator and operates on boolean operands. If both the operands are true, then the condition becomes true otherwise it is false. Assume boolean variable A holds true and variable B holds false then (A && B) is false.& is to be used during bitwise operations and && is useful during logical operations.
Read MoreJava Boolean operators
There are following boolean operators supported by Java language.Assume variable A holds 10 and variable B holds 20, then −OperatorDescriptionExample== (equal to)Checks if the values of two operands are equal or not, if yes then condition becomes true.(A == B) is not true.!= (not equal to)Checks if the values of two operands are equal or not, if values are not equal then condition becomes true.(A != B) is true.> (greater than)Checks if the value of left operand is greater than the value of right operand, if yes then condition becomes true.(A > B) is not true.< (less than)Checks if the ...
Read Morehow to convert Object array to String array in java
As list.toArray() returns an Object[], it can be converted to String array by passing the String[] as parameter. See the example below.import java.util.ArrayList; import java.util.List; public class Tester { public static void main(String[] args) { List data = new ArrayList(); data.add("A"); data.add("B"); data.add("C"); //Object[] objects = data.toArray(); String[] strObjects = data.toArray(new String[0]); for(String obj: strObjects) { System.out.println(obj); } } }OutputA B C
Read Moreremove null value from a String array in Java
Following program creates an array with null values. Convert it a list with not-null values only and then get the array of that list.Exampleimport java.util.ArrayList; import java.util.List; public class Tester { public static void main(String[] args) { String[] array = {"I", null, "love", null, "Java" }; List values = new ArrayList(); for(String data: array) { if(data != null) { values.add(data); } } String[] target = values.toArray(new String[values.size()]); for(String data: target) { System.out.println(data + " "); } } }OutputI love Java
Read MoreHow to convert List to int[] in Java?
You can simply iterate through list and fill the array as shown below −import java.util.ArrayList; import java.util.List; public class Tester { public static void main(String[] args) { List list = new ArrayList(); list.add(new Integer(1)); list.add(new Integer(2)); list.add(new Integer(3)); list.add(new Integer(4)); int[] array = new int[list.size()]; for(int i=0;i
Read MoreJava string concat() method vs "+" operator
The notable differences between concat() method and +operator are:concat() method+operatorYou cannot concat a null value to a String using the concat() method.You can concat null value using the ‘+’ operator.Using the concat() method you can concat only two String variables.Using the ‘+’ operator you can concat multiple values.Using the concat() method you can concat only String type of arguments.Using the ‘+’ operator you can concat any type of arguments.
Read MoreWhat is string constant pool in Java?
When you store a String asString str1 = "Hello";directly, then JVM creates a String object with the given value in a separate block of memory known as String constant pool.And whenever we try to create another String asString str2 = "Hello";JVM verifies whether any String object with the same value exists in the String constant pool, if so, instead of creating a new object JVM assigns the reference of the existing object to the new variable.And when we store String asString str = new String("Hello");using the new keyword, a new object with the given value is created irrespective of the ...
Read MoreChecking for Null or Empty or White Space Only String in Java.
We can verify whether the given string is empty using the isEmpty() method of the String class. This method returns true only if length() is 0. Example import java.lang.*; public class StringDemo { public static void main(String[] args) { String str = "tutorialspoint"; // prints length of string System.out.println("length of string = " + str.length()); // checks if the string is empty or not System.out.println("is this string empty? = " + str.isEmpty()); } } Output length of string = 14 is this string empty? = false
Read MoreConstructors of StringBuilder class in Java.
The StringBuilder class of the java.lang package is a mutable sequence of characters. This provides an API compatible with StringBuffer, but with no guarantee of synchronization. Following are the list of constructors provided by the StringBuilder class.S.N.Constructor & Description1StringBuilder()This constructs a string builder with no characters in it and an initial capacity of 16 characters.2StringBuilder(CharSequence seq)This constructs a string builder that contains the same characters as the specified CharSequence.3StringBuilder(int capacity)This constructs a string builder with no characters in it and an initial capacity specified by the capacity argument.4StringBuilder(String str)This constructs a string builder initialized to the contents of the specified string. ...
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