Below is the explanation of the steps involved:
sample.java → javac (sample. class) → JVM(sample.obj) → final output
First source code is used by java compiler and is converted in .class file. The class file code is in byte code form and that class file is used by JVM to convert into an object file. After that, you can see the final output on your screen.
Moving ahead in Java architecture article, let us understand the concept of JIT in Java.
JIT in Java
Just In Time compiler commonly known as JIT, is basically responsible for performance optimization of java based applications at run time. The performance of an application is dependent on a compiler.
Here is a simple diagram showing you the internal process going on.
sample.java → javac (sample. class) → JVM(sample.obj) → final output
First source code is used by java compiler and is converted in .class file. The class file code is in byte code form and that class file is used by JVM to convert into an object file. After that, you can see the final output on your screen.
Moving ahead in Java architecture article, let us understand the concept of JIT in Java.
JIT in Java
Just In Time compiler commonly known as JIT, is basically responsible for performance optimization of java based applications at run time. The performance of an application is dependent on a compiler.
Here is a simple diagram showing you the internal process going on.
The JIT compiler compiles the byte code of the method into machine code, compiling it “Just In Time” to run. When a method is compiled, the JVM calls the compiled code of that method directly.
Let’s dive deeper:
The byte code has to be interpreted or compiled to proper machine instructions depending on the instruction set provided. Also, these can be directly executed if the instruction architecture is byte code based. Interpreting the byte code affects the speed of execution.
In order to improve performance, JIT compilers interact with the Java Virtual Machine (JVM) at run time and compile suitable bytecode sequences into native machine code (as shown in the diagram). While using a JIT compiler, the hardware is able to execute the native code, as compared to having the JVM interpret the same sequence of bytecode repeatedly and incurring overhead for the translation process.
Let’s dive deeper:
The byte code has to be interpreted or compiled to proper machine instructions depending on the instruction set provided. Also, these can be directly executed if the instruction architecture is byte code based. Interpreting the byte code affects the speed of execution.
In order to improve performance, JIT compilers interact with the Java Virtual Machine (JVM) at run time and compile suitable bytecode sequences into native machine code (as shown in the diagram). While using a JIT compiler, the hardware is able to execute the native code, as compared to having the JVM interpret the same sequence of bytecode repeatedly and incurring overhead for the translation process.
What are Comments in Java?
Single-line comments
Multi-line comments
Documentation comments
Single-line comments
Multi-line comments
Documentation comments
Comments in Java are often are non-executable statements, used to understand the code better and to make it more readable. As mentioned above, it can also be helpful in preventing code execution when testing an alternative code. In short, Java comments are non-executable statements, used to understand Code better.
Single-line Comments
This type of comment is mainly used for describing the code functionality. It is the easiest typed comments. Single-line comments start with two forward slashes (//). Any text between // and the end of the line is ignored by Java implies it will not be executed. Now, let’s take a small example to know how single-line comments can be used.
This type of comment is mainly used for describing the code functionality. It is the easiest typed comments. Single-line comments start with two forward slashes (//). Any text between // and the end of the line is ignored by Java implies it will not be executed. Now, let’s take a small example to know how single-line comments can be used.
You can see in the above example that I have used single-line comments to comment on the specific lines in a program. That’s how it works. Now, let’s understand what are multi-line comments.
Multi-line Comments
To describe a full method in a code or a complex snippet single line comments can be tedious to write since we have to give ‘//’ at every line. So to overcome this multi-line comments can be used. Multi-line comments start with /* and end with */. Any text between /* and */ will be ignored by Java. It is used to comment multiple lines of code.
Now, let’s take a small example to know how multi-line comments can be used.
To describe a full method in a code or a complex snippet single line comments can be tedious to write since we have to give ‘//’ at every line. So to overcome this multi-line comments can be used. Multi-line comments start with /* and end with */. Any text between /* and */ will be ignored by Java. It is used to comment multiple lines of code.
Now, let’s take a small example to know how multi-line comments can be used.
You can see in the above example I have used multi-line comments to comment on the lines in a program. That’s how it works. Now, let’s understand what is documentation comments.
Documentation Comments
This type of comments is used generally when you are writing code for a project/ software package. It helps you to generate a documentation page for reference, which can be used for getting information about methods present, its parameters, etc.
This type of comments is used generally when you are writing code for a project/ software package. It helps you to generate a documentation page for reference, which can be used for getting information about methods present, its parameters, etc.
What are Java Keywords and reserved words?
Keywords are predefined which have a unique meaning and functionality in Java programming language. These keywords are also known as reserved keywords which mean they cannot be used as a variable name, class, method or any other identifier. There are 57 reserved keywords in Java. Meanwhile, in this huge list of java keywords, there are some which are not used anymore and few versions do not support a tiny number of keywords.
Keywords are predefined which have a unique meaning and functionality in Java programming language. These keywords are also known as reserved keywords which mean they cannot be used as a variable name, class, method or any other identifier. There are 57 reserved keywords in Java. Meanwhile, in this huge list of java keywords, there are some which are not used anymore and few versions do not support a tiny number of keywords.
What is a Constructor in Java?
We create a constructor to initialize an object. They have the same name as the class but have no explicit return type. It can be used to set initial values for object attributes. It is similar to a Java method
At the time of calling the constructor, the memory is allocated for the object. Each class in Java has a constructor. Even if you do not create one, Java implicitly calls a constructor with all data members value set to zero.
We create a constructor to initialize an object. They have the same name as the class but have no explicit return type. It can be used to set initial values for object attributes. It is similar to a Java method
At the time of calling the constructor, the memory is allocated for the object. Each class in Java has a constructor. Even if you do not create one, Java implicitly calls a constructor with all data members value set to zero.
When is a Constructor Called?
A constructor is called when an object or an instance is created. It is used to assign values to the data members of the same class.
Rules For Constructors in Java
1 The name of the constructor should be the same as that of the class name.
2 A constructor cannot be declared as final, static, synchronized or abstract.
3 It cannot have an explicit return type.
4 A constructor can have an access modifier to control the access.
You should follow these rules while creating a constructor.
Types of Constructors in Java
There are two types of constructors
1 Default Constructor
2 Parametrized Constructor
Default Constructor
A constructor with no arguments is called a default constructor. If we do not create a constructor of a class, Java creates a default constructor with data members which has values like zero, null, etc.
But, if we specify a constructor with no arguments, it will be a default constructor or a no argument constructor which is another name for default constructor. Following is an example to show how to use a default constructor in Java:
A constructor is called when an object or an instance is created. It is used to assign values to the data members of the same class.
Rules For Constructors in Java
1 The name of the constructor should be the same as that of the class name.
2 A constructor cannot be declared as final, static, synchronized or abstract.
3 It cannot have an explicit return type.
4 A constructor can have an access modifier to control the access.
You should follow these rules while creating a constructor.
Types of Constructors in Java
There are two types of constructors
1 Default Constructor
2 Parametrized Constructor
Default Constructor
A constructor with no arguments is called a default constructor. If we do not create a constructor of a class, Java creates a default constructor with data members which has values like zero, null, etc.
But, if we specify a constructor with no arguments, it will be a default constructor or a no argument constructor which is another name for default constructor. Following is an example to show how to use a default constructor in Java: