Throws Exception – throws Keyword The designer of a class knows very well, the problems that may occur while using the methods or constructors of the class, he designed. If the methods are used by another programmer, the question is how the designer informs the programmer, the possible problems that may occur while using the …
Introduction to thread group and grouping of threads We know earlier, every thread should belong to some thread group and if no group is mentioned, the thread is placed, by default, in main thread group. When the JVM starts a new process, it creates main thread group and every thread created by the programmer, if …
Introduction to Thread Priority/h6> Thread scheduling of waiting threads, to the processor, is done by the thread scheduler. Thread scheduler is part of the OS and different operating systems come with different scheduling algorithms. When some threads are to be executed before the other, a programmer can give priorities to the threads. As per the …
JAR Java ARchive Files Introduction JAR is an acronym for Java ARchive. It is the zipping technique of Java. Always, the zipping styles are platform-dependent. A WinZip file can be zipped and unzipped on Windows platform only. The Java files, which are platform-independent, zipped with WinZip makes them platform-dependent (opens on Windows platform only). To …
Creating an object of a Class without using new Keyword It is of general practice to create an object with new keyword. It is also possible to create an object without new keyword. This is of logical significance only and not used in regular practice. public class Hello { public void display() { System.out.println(“Hello World”); …
Introduction The java.lang.Character class includes many useful static methods with which text (or characters) can be manipulated. The other text manipulating classes are String, StringBuffer, StringTokenizer and StringBuilder. The Character class is a wrapper class for char data type. That is, a Character object represents char as an object; it gives an object form to …
isDaemon isAlive isInterrupted getThreadGroup Summary: So far, we studied the methods like sleep(), start() and currentThread() etc. of Thread class. Let us study some more, very less used by the Programmers, like methods isDaemon isAlive isInterrupted getThreadGroup etc. Program with Methods isDaemon isAlive isInterrupted getThreadGroup : public class MoreMethods { public static void main(String args[]) …
Introduction The instanceof keyword is very useful to know whether an object belongs to which class. The instanceof evaluates to true if an object belongs to a specified class or its super class; else raises compilation error. The following program illustrates. public class InstanceDemo { public static void main(String args[]) { String s1 = “hello”; …
Java Versions or JDK Versions What is Java Version? Java is not developed by a single man, but developed by a team of engineers belonging to the corporate giant Sun Microsystems. The development never ends; it goes on. The engineers at Sun Microsystems watch the market demands everyday and adds more classes to the existing …
Java Create Threads Threads can be created in two ways in Java. By extending Thread class. By implementing Runnable interface. Why Java requires two types and when to use which type, we will see later. Signature of Thread class public class Thread extends Object implements Runnable Observe, the Thread class implements Runnable interface. 1. Creating …
try catch finally – The finally Block We know earlier, there should be a successful handler in the catch block like ArithmeticException for division by zero and ArrayIndexOutOfBoundsException for wrong array index number etc. Placing a wrong handler is equivalent to not having a try-catch block at all. There may be some statements which must …
Java permits the creation of user defined exceptions as per the needs of coding. To use it Developer uses throw keyword. Explained in simple terms, examples and screenshots to Beginner in this tutorial "throw keyword User defined Exception". Using throw Keyword To display a message, a number of ways exist in Java (in C, it …
Two separate examples given on HTML to Applet communication in 1st page and Applet to Applet communication in 3rd page. HTML to Applet: Reading from HTML into Applet Sometimes, it may be required to initialize some data while the applet object is being created. This data may be useful to give the properties to the …
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Loading and Running Images Images, audio clips and animation requires special focus as all the images are not drawn at a time. Either image drawing or downloading takes a long time as part by part is written or downloaded. Here, we use mainly two methods – one that creates an image object and the other …
We know earlier, the + operator is implicitly overloaded in Java – works for addition and concatenation. For concatenation, String class includes concat() method. That is, strings can be concatenated both with + operator an concat() method. Following program illustrates. public class Concat { public static void main(String args[]) { String s1 = “to”; String …
hashCode() vs equals(): About Hash code hashCode() is a method of Object class. Hash code is an integer representation of an object by JVM. Hash code is system generated using some formula (let us not go much of detais of formula). Hash codes generated need not be the same for different times of execution. Internally, …
Introduction Object class has got very prominence in Java programming. In inheritance, it sits at the top of the hierarchy. That is, any Java class, either you write or predefined, should be a subclass of Object class. If you write any class, Java implicitly extends Object class. Why this? Java designers thought that some methods …
About toString() method Summary: Java comes with two styles of converting object into string form. "toString() method Convert Object to String form" discusses using toString() method. We discussed toString() method in String class to some extent. Let us go more detailed here. toString() of Object class converts only objects into string form (remember, valueOf() of …
Java Abstract Class Tutorial Example Summary: By the end of this tutorial "Java Abstract Class Tutorial Example", you will be comfortable to practice abstract methods and abstract classes. abstract Modifier You have seen earlier two access modifiers – static and final. Now let us go for another modifier "abstract". "abstract" modifier (and also keyword) can …
GregorianCalendar is a concrete class, a subclass of abstract class Calendar. The GregorianCalendar class represents the calendar we use everyday. It is used to manipulate date and retrieve date particulars. This was introduced with JDK 1.1. Following statement gives the class signature public class GregorianCalendar extends Calendar Following program illustrates the usage of a few …