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By Java Tutor, on October 3rd, 2011 Though constructors and methods look similar to each other, they are different both in construct and syntax.
Constructors are used to create instances of a class. Constructors are created in a manner similar to objects, such as:
mari_gold m_var1= new mari_gold();
Some of the key properties that differentiate the constructor and the methods are:
- Modifiers: Like methods, constructors can also use any of the following three access modifies, such as Public, Private, and non, which is also known as package or friendly. The following types of constructors do not exist: abstract, abstract, static, final, native, or synchronized.
- Return types: Constructors do not have any kind of return types, unlike methods which can have any valid return type or at least a default value as void.
- Signature: The naming convention of constructors and methods also vary greatly. Constructors get the same name as the class name. On the other hand, methods use names that are not same as class name. If the programmers use the normal Java language conventions, constructors would always start with upper case letters, unlike methods which start with a lower case letter. Not only this, you will also notice that the names of the constructors are nouns, whereas the method names are adjectives as they indicate action.
- The use of “This” keyword: Both constructors and methods use the keyword “this” in a different manner. The keyword ‘this’ in a method refers to an instance of the class that is using the method. Also, the static methods do not belong to any instance of the class, and therefore the keyword “this” does not refer to anything in such methods. These methods belong to an entire class and not to any particular instance of the class.
Conversely, in the case of constructors, to refer to another constructor in the same class the “this” keyword is used, but having a different list of the parameters associated with it. Continue reading JAVA – Constructors
By Java Tutor, on September 29th, 2011
A method can be defined as a group of instructions that is given a name and can be called up anywhere in the program code by simply calling it by its name. For instance, a statement to draw a straight line can be given a name straight_line. You can then call the straight_line statement thrice to draw a triangle or you could save the method triangle and call it as and when required.
All programming languages support methods presumably by different names such as functions or procedures. The Java language, just like the C++ language from which it originated, supports methods. Unlike the C++ language where an object can contain methods, the Java programming language declares a program which further contains functions known as methods. As you will notice, the method is declared in a similar manner as the method paint, the only difference being that the method paint is automatically called.
The code snippet below displays a simple method, calculate.
import java.awt.*;
import java.applet.*;
public class calculate_value extends Applet
{ int first_var, answer_var_1;
public void paint_function (Graphics graph_var)
{
First_var = 34;
Calculate_value();
g.draw_String(“Twice 46 is ” + answer_var_1, 50, 75);
}
public void calculate_value ()
{ answer_var_1 = first_var * 8;
}
}
As you can see, the method calculate_value is called by the statement calculate_value();. The syntax of the method requires the use of opening and closing braces after the method name (even they don’t contain anything) followed by a semicolon at the end.
However, it is just not enough to call a method. However, it is important to define a method before it is called. Else, the Java programming language will not know what to do when it encounters a method name. The method definition always starts with the public or private keyword. Continue reading JAVA – Methods
By Java Tutor, on September 25th, 2011 The Java programming language uses certain fundamental elements such as numbers, characters, and Boolean values. These programming elements are not considered as objects in this language. Java supports the concept of wrapper classes in situations where a primitive value needs to be treated as an object. This helps the Java compiler optimize the performance of these objects.
The java Virtual Machine architecture helps define the precise or exact values of the primitive types. For example, according to this architecture, int is always defined as a 32-bit signed two digit compliment number. Some other types that can be defined in this manner are
- Boolean
- char
- byte
- short
- int
- long
- float
- double
These primitive types resemble the scalar types of the C programming language on a 32-bit machine that is byte oriented. The new programmers of Java language can use these data types to learn the language faster and with greater ease. Continue reading JAVA – Primitive Types
By Java Tutor, on September 21st, 2011 The term data element refers to the smallest unit of data having a specific meaning associated with it and defined using a particular syntax. Some of the characteristics of data element are:
- A data element has its own identification and is recognized by the same, such as the name of the data element.
- They need to be clearly defined
- The data elements consist of one or more terms used to represent this data element, also known as the representation terms.
- A data element has some values associated with it in detail, also known as code.
You can use data elements when developing software applications or application data files. Use the process of Application discovery and understanding to discover data elements. Next, register these data elements in the metadata registry.
By Java Tutor, on May 17th, 2011 A class can be defined as a collection of named fields and codes organized into methods that are named according to proper syntax and operating on a particular set of data. These fields and methods that are part of a collection are termed as members of the class. Not only this, in Java, a class may contain other classes also.
The static members of the class are associated with the class itself. On the other hand, the instance members of the class are associated with separate objects or instances of the class.
The member of a class can be divided into the following categories:
- Class fields
- Class methods
- Instance fields
- Instance methods
The code snippet given below displays the class definition for the class Circle. Not that this class contains all the four members of the class Circle
public class Circle
{
// Here is an example of a field of a class
public static final double value_of_PI= 3.14159; // Note that PI has a fixed constant value used in math
// Here is an example of a method of a class which computes the value of a circle value based on the arguments
Continue reading JAVA Classes – The Members of a Class
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