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Following example is converting a String to int.ExampleLive Demopublic class Tester { public static void main(String[] args) { String intString = "1234"; int value = new Integer(intString).intValue(); System.out.println(value); } }Output1234
Just as you can pass primitive type values to methods, you can also pass arrays to methods. For example, the following method displays the elements in an int array -Examplepublic static void printArray(int[] array) { for (int i = 0; i < array.length; i++) { System.out.print(array[i] + " "); } }You can invoke it by passing an array. For example, the following statement invokes the print Array method to display 3, 1, 2, 6, 4, and 2 -printArray(new int[]{3, 1, 2, 6, 4, 2});
NullPointerException is a runtime exception and it is thrown when the application try to use an object reference which has a null value.For example, using a method on a null reference.Object ref = null; ref.toString(); // this will throw a NullPointerException
You should get a start time before making a call and end time after method execution. The difference is the time taken. ExampleLive Demoimport java.util.Calendar; public class Tester { public static void main(String[] args) { long startTime = Calendar.getInstance().getTimeInMillis(); longRunningMethod(); long endTime = Calendar.getInstance().getTimeInMillis(); System.out.println("Time taken: " + (endTime - startTime) + " ms"); } public static void longRunningMethod() { try { Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } } }OutputTime taken: 1012 ms
From Java 8 onwards, the lambda expression is introduced which acts as function pointers.Lambda expressions are introduced in Java 8 and are touted to be the biggest feature of Java 8. Lambda expression facilitates functional programming and simplifies the development a lot.SyntaxA lambda expression is characterized by the following syntax.parameter -> expression bodyFollowing are the important characteristics of a lambda expression.Optional type declaration − No need to declare the type of a parameter. The compiler can inference the same from the value of the parameter.Optional parenthesis around parameter − No need to declare a single parameter in parenthesis. For multiple ... Read More
Let us look at a simple code that will print the words Hello World.ExampleLive Demopublic class MyFirstJavaProgram { /* This is my first java program. * This will print 'Hello World' as the output */ public static void main(String []args) { System.out.println("Hello World"); // prints Hello World } }Let's look at how to save the file, compile, and run the program. Please follow the subsequent steps −Open notepad and add the code as above.Save the file as: MyFirstJavaProgram.java.Open a command prompt window and go to the directory where you saved the class. Assume ... Read More
A class, method, constructor, interface, etc. declared public can be accessed from any other class. Therefore, fields, methods, blocks declared inside a public class can be accessed from any class belonging to the Java Universe.However, if the public class we are trying to access is in a different package, then the public class still needs to be imported. Because of class inheritance, all public methods and variables of a class are inherited by its sub classes.ExampleThe following function uses public access control -public static void main(String[] arguments) { // ... }The main() method of an application has to be ... Read More
Variables, methods, and constructors, which are declared protected in a superclass can be accessed only by the subclasses in other package or any class within the package of the protected members' class.The protected access modifier cannot be applied to class and interfaces. Methods, fields can be declared protected, however methods and fields in a interface cannot be declared protected.Protected access gives the subclass a chance to use the helper method or variable, while preventing a non-related class from trying to use it.ExampleThe following parent class uses protected access control, to allow its child class override openSpeaker() method - class AudioPlayer ... Read More
Default access modifier means we do not explicitly declare an access modifier for a class, field, method, etc.A variable or method declared without any access control modifier is available to any other class in the same package. The fields in an interface are implicitly public static final and the methods in an interface are by default public.ExampleVariables and methods can be declared without any modifiers, as in the following examples -String version = "1.5.1"; boolean processOrder() { return true; }
Methods, variables, and constructors that are declared private can only be accessed within the declared class itself.Private access modifier is the most restrictive access level. Class and interfaces cannot be private.Variables that are declared private can be accessed outside the class, if public getter methods are present in the class.Using the private modifier is the main way that an object encapsulates itself and hides data from the outside world.ExampleThe following class uses private access control - public class Logger { private String format; public String getFormat() { return this.format; } public void setFormat(String ... Read More