In this section, we will learn how to write the simple program of Java. We can write a simple hello Java program easily after installing the JDK. To create a simple Java program, you need to create a class that contains the main method. Let's understand the requirement first. For executing any Java program, the following software or application must be properly installed.
When we compile Java program using javac tool, the Java compiler converts the source code into byte code. Let's see what is the meaning of class, public, static, void, main, String[], System.
It means it is visible to all. If we declare any method as static, it is known as the static method. The core advantage of the static method is that there is no need to create an object to invoke the static method. The main method is executed by the JVM, so it doesn't require creating an object to invoke the main method. So, it saves memory. It means it doesn't return any value.
String[] args or String args[] is used for command line argument. We will discuss it in coming section. Here, System is a class, out is an object of the PrintStream class, println is a method of the PrintStream class. We will discuss the internal working of System. As displayed in the above diagram, write the simple program of Java in notepad and saved it as Simple. When we have done with all the steps properly, it shows the following output:. Write here:. There are many ways to write a Java program.
The modifications that can be done in a Java program are given below:. Check Leap Year Or Not Prime Number Java Program Reverse A String In Java 2.
Reverse An Array Program 5. Insert An Element in Array 6. Linear Search In Java some text some text. Sort Programs. Conversion Programs:. Convert Octal To HexaDecimal 2. Convert Decimal To Hexadecimal 3. Convert Decimal To Octal 4. Convert Decimal To Binary 5. Convert Fahrenheit To Celsius. Invert Pyramid Star Pattern 6. Hollow Right Triangle Star Pattern 7. Hollow Rhombus Star Pattern 8. X Star Pattern 9. Square Star Pattern Right Arrow Star Pattern Rhombus Star Pattern Pyramid Star Pattern Plus Star Pattern Mirrored Right Triangle Left Arrow Star Pattern Hollow Diamond Star Half Diamond Star Pattern Program Inverted Right Triangle Star Hollow Inverted Pyramid Star Pattern Hollow Pyramid Star Hollow Inverted Mirrored Right Triangle Inverted Mirrored Right Triangle Hollow Mirrored Right Triangle Hollow Rhombus Pattern Inverted Pyramid Star Pattern.
Functions of JVM:. We know that JVM converts the class file into its equivalent executable code. Now if a JVM is in windows environment executable code that is understood by windows environment only.
Java, With the help of this course, students can now get a confidant to write a basic program to in-depth algorithms in C Programming or Java Programming to understand the basics one must visit the list Java programs to get an idea.
But the platform dependency of the JVM is not considered while saying Java is platform independent because JVM is supplied free of cost through the internet by the sun microsystems. Platform independence :.
Compiled code of a program should be executed in any operating system, irrespective of the as in OS in which that code had been generated. This concept is known as platform independence. Note: In structured programming lang programs, the global variable play a vital role. But because of these global variables, there is data insecurity in the structured programming lang programs.
In this way data is unsecured. But this is not the actual reason. Assume that it is a project. Now if any upgradation is required, then the client i. Now we should note that it is not guaranteed that the programmers who developed this program will still be working with that company. Hence this project falls into the hands of new programmers. Automatically it takes a lot of time to study. The project itself before upgrading it. It may not be surprising that the time required for writing the code to upgrade the project may be very less when compared to the time required for studying the project.
If the new programmer adds a new function to the existing code in the way of upgrading it, there is no guarantee that it will not affect the existing functions in the code.
This is because of global variables. In this way, data insecurity is created. Three of the global variables may be used only by two functions. But in a structured prog. To avoid this problem, programmers have designed a way such that the variables and the functions which are associated with or operate on those variables are enclosed in a block and that bock is called a class and that class and that class is given a name, Just as a function is given a name.
Now the variables inside the block cannot be called as the local variable because they cannot be called as global variables because they are confined to a block and not global. Hence these variables are known as instance variables. Therefore a class is nothing but grouping data along with its functionalities.
Encapsulations came into existence in order to provide security for the data present inside the program. Note 2: Any object oriental programming language file looks like a group of classes. Everything is encapsulated. Nothing is outside the class. EX: c- language Java follows the Dynamic loading — JVM would not convert all the statements of the class file into its executable code at a time.
Java Programs Hello World. Area Of Circle Java Program. Area Of Triangle. Create and call a method Call a method multiple times Method with parameters Method with multiple parameters Return value A method with if Create a class and an object of a class Create multiple objects of a class Accessing class attributes variables Modify attributes Override existing attribute values Multiple attributes Create a class method Method with parameters Access class methods with an object Create a class constructor Constructor with parameters.
Public class Default class Public attributes Private attributes Default attributes Protected attributes Final class Abstract class with abstract methods. Java encapsulation getters and setters. Java inheritance extends Java polymorphism. Inner class Private inner class error when trying to access it from an outside class Static inner class Access outer class from inner class. Java abstract classes and methods Java interface implements Multiple interfaces. Create an enum with a group of constants An enum inside a class An enum in a switch statement Loop through an enum.
Read user input Read user input of various types. Display current date Display current time Display current date and time Formatting date and time. Getting an iterator Looping throug a collection Removing items from a collection.
Create an ArrayList that should store numbers integers Create wrapper objects Using wrapper methods Convert wrapper objects to strings. The try
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