System.out.println() in Java

System.out.println() is a main method applied in the console output, provided when debugging and for user instructions purposes. It is part of the System class of the java.lang package, and it is inherited by all Java programs without importing any packages. Here's a breakdown of each component.

System: This class is part of the Java standard library (java.lang package) that provides the standard input, standard output, error output data streams, and similar system resources.

out: This is a regular and class System attribute, being the system output stream. It's an example of PrintStream (Interface providing the capability for putting data into various output streams).

println(): This means the PrintStream object is doing the task. Here is an example that outputs "Hi, World!" to System.out. The println() method tries the data along with a newline character that comes by default, so it can be used to display messages in a readable way. Usually, a method is invoked by objectname.methodname().

But we cannot create the object to the PrintStream class directly, as above. So, Java provides an alternative way to create the object of PrintStream class that is System.out.

Where System is the class name, it is declared as final. The out is an instance of the System class and is of type PrintStream. Its access specifiers are public and final. It is an instance of java.io.PrintStream. When we call the member, a PrintStream class object creates internally.

So, we can call the print() method, as shown below:

It creates the PrintStream class object. This object, by default, represents the output device, i.e., the monitor.

Example

In the following example, we have used two print() methods, which gives the result in one line. It means the first print() method displays the string "Hello!" and retains the cursor at the same line. The second print() method also displays the string "Java" at the same line adjacent to the previous string.

PrintExample.java

Output

Hello!Java

Java println() method

The println() method is similar to print() method except that it moves the cursor to the next line after printing the result. It is used when you want the result in two separate lines. It is called with "out" object.

If we want the result in two separate lines, then we should use the println() method. It is also an overloaded method of PrintStream class. It throws the cursor to the next line after displaying the result.

Example

The following example, the println() method display the string in two separate lines.

Demo.java

Output

Hello!
Java

Difference Between print() and println() Methods

Both methods are used to display the results on the monitor. The print() method displays the result on the console and retains the cursor in the same line. It works only with an argument. The println() method also displays the result on the console but moves the cursor to the next line. It can also work without arguments.

PrintExample.java

Output:

Hello, world!How are you?
I'm fine, thank you!

Just like System.out for standard output, there are two other standard streams: System.in and System.err, known as standard input and standard error, respectively.

System.in:

System.in is an instance of the InputStream class.

It usually corresponds to the input from the keyboard.

It enables you to get data from a standard input stream, for example, user inputs during runtime.

You can use classes such as Scanner or BufferedReader together with System.in to read input from the user.

System.err:

System.err is a PrintStream object like System.out.

It is the symbol for the standard error output stream.

It is used to print error messages, diagnostics, and any other related information that connotes an error.

Unlike System.out, System.err is usually utilized for reporting errors and is not redirected by default when you redirect standard output.