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Object Oriented Programming Articles
Page 199 of 589
How is down-casting possible in Java?
Yes, a variable can be downcast to its lower range substitute by casting. It may lead to data loss although. See the example below −Examplepublic class Tester { public static void main(String[] args) { int a = 300; byte b = (byte)a; System.out.println(b); } }OutputIt will print output as −44
Read MoreHow to import java.lang.String class in Java?
To import any package in the current class you need to use the import keyword asimport packagename;Exampleimport java.lang.String; public class Sample { public static void main(String args[]) { String s = new String("Hello"); System.out.println(s); } }OutputHello
Read MoreString Concatenation by concat() method.
You can concatenate two strings using the concat() method of the String class. This class concatenates the specified string to the end of this string.Examplepublic class Test { public static void main(String args[]){ String str1 = "Krishna"; String str2 = "Kasyap"; System.out.println(str1.concat(str2)); } }OutputkrishnaKasyap
Read MoreLocal variables in Java
Local variables are declared in methods, constructors, or blocks.Local variables are created when the method, constructor or block is entered and the variable will be destroyed once it exits the method, constructor, or block.Access modifiers cannot be used for local variables.Local variables are visible only within the declared method, constructor, or block.Local variables are implemented at stack level internally.There is no default value for local variables, so local variables should be declared and an initial value should be assigned before the first use.ExampleHere, age is a local variable. This is defined inside pupAge()method and its scope is limited to only ...
Read MoreMember variables in Java
Member variables are known as instance variables in java.Instance variables are declared in a class, but outside a method, constructor or any block.When space is allocated for an object in the heap, a slot for each instance variable value is created.Instance variables are created when an object is created with the use of the keyword 'new' and destroyed when the object is destroyed.Instance variables hold values that must be referenced by more than one method, constructor or block, or essential parts of an object's state that must be present throughout the class.Instance variables can be declared in a class level ...
Read MoreInstance variables in Java
Instance variables are declared in a class, but outside a method, constructor or any block.When space is allocated for an object in the heap, a slot for each instance variable value is created.Instance variables are created when an object is created with the use of the keyword 'new' and destroyed when the object is destroyed.Instance variables hold values that must be referenced by more than one method, constructor or block, or essential parts of an object's state that must be present throughout the class.Instance variables can be declared at the class level before or after use.Access modifiers can be given ...
Read MoreFind the 3rd smallest number in a Java array.
ExampleFollowing is the required program.public class Tester { public static int getThirdSmallest(int[] a) { int temp; //sort the array for (int i = 0; i < a.length; i++) { for (int j = i + 1; j < a.length; j++) { if (a[i] > a[j]) { temp = a[i]; a[i] = a[j]; a[j] = temp; } } } //return third smallest element return a[2]; } public static void main(String args[]) { int a[] = { 11,10,4, 15, 16, 13, 2 }; System.out.println("Third Smallest: " +getThirdSmallest(a)); } }OutputThird smallest: 10
Read MoreA closer look at Java "Hello World" program
Let us look at a simple code that will print the words Hello World.Examplepublic 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 it's ...
Read MoreWhy can't we define a static method in a Java interface?
From Java 8 onwards, static methods are allowed in Java interfaces.An interface can also have static helper methods from Java 8 onwards. public interface vehicle { default void print() { System.out.println("I am a vehicle!"); } static void blowHorn() { System.out.println("Blowing horn!!!"); } }Default Method ExampleCreate the following Java program using any editor of your choice in, say, C:\> JAVA.Java8Tester.javapublic class Java8Tester { public static void main(String args[]) { Vehicle vehicle = new Car(); vehicle.print(); } } interface Vehicle { default void print() { ...
Read MoreHow do I time a method execution in Java
You should get a start time before making a call and end time after method execution. The difference is the time taken. Exampleimport 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
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