Introduction
The statement System.out.println() is a fundamental piece of code in Java programming, often used for outputting ( printing ) information to the console.
Let’s delve deeper into its meaning and functionality..
Syntax
System.out.println(argument);
The argument could be anything: a number ( integer, float, double ), a word, or a sentence.
Diving deeper into the meaning
System :
This is a predefined final class in Java’s core library (java.lang package) that provides access to system-related properties and methods.
System is a final class as it cannot be extended. A class is made final when we need to avoid alteration of base behavior due to the class being extended.
out :
This is a static member of the System class, referring to the standard output stream.
Being static allows the out variable to be accessed directly without the need to create an instance of its class (in our case the System class). This makes it convenient to access the standard output stream from anywhere in your code without having to instantiate System.
Like out, the system class has other members :
in :
System.in refers to an InputStream connected to a standard console to get input, typically a keyboard.
Both System.in, and System.out are initialized when a Java VM starts by the Java runtime.
println() :
This is a method of the PrintStream class, which is responsible for printing data to the output stream.
System class has a public and static member field called PrintStream.
All instances of the class PrintStream have a public method called println().
By declaring it as public, it can be accessed from any other class or package within the Java runtime environment. This means that any Java code, regardless of its location in the program, can make use of System.out.println() for outputting information to the standard output stream.
Difference between println() and print()
println() :
The println() method is specifically designed to print the provided data followed by a newline character, so each subsequent call to println() will print its argument on a new line.
public class Main {
public static void main(String[] args) {
System.out.println("Hello");
System.out.println("world!");
}
}
output:
Hello
world!
print() :
The print() method is designed only to print the provided data without adding a newline character.
public class Main {
public static void main(String[] args) {
System.out.print("Hello");
System.out.print("world!");
}
}
output:
Helloworld!
Shortcut for System.out.println()
Static import of java.lang.System.out will remove the need for the “System.” part of the statement.
import static java.lang.System.out;
public class Main {
public static void main(String[] args) {
out.println("Hello, world!"); // No need for "System." prefix
}
}
However, the static import isn’t recommended as it decreases code readability.
Keyboard shortcuts
In IDEs like Eclipse, shortcuts like Ctrl+Spacebar can help you be quick while using the statement.
While in VSCode, you can type sout and press enter, it will print the statement for you!