Print Statements and Comments
Let the Program Speak!
Let’s try to write a program that says Hello World out by typing the line of code System.out.print("Hello World");
The program prints out whatever you typed in the parenthesis of System.out.print. And, each line of code ends with ;.
After, add more statements to print numbers by putting numbers in the parenthesis (i.e. System.out.print(2020)) or a symbol by putting one symbol between 2 single quotes ' (i.e. System.out.print('@')).
Did you notice that all the statements you typed printed in one line?
Sometimes we want to enter a new line when typing.
To do that, we type a slightly different code System.out.println();
(Note: we type println instead of print to create a new line after)
Go back up and give it a try. Make all the statements print on different lines!
How to print multiple symbols in one line of code?
We learned that to print symbols we put them around 2 single quotes ', but how do we print multiple symbols in one line?
We can simple put them between 2 double quotes " (i.e. System.out.print("@ , - h A #");)
!! Important !! Sometimes you can’t just put characters in between " "
When putting characters in between " " in a print statement, sometimes it’s easy to confuse the computer on what characters to print.
For example, how do we tell computer to print "?
If you type System.out.print(""");, you will get an error! because the computer can’t identify where the text ends!
Instead, certain characters need to be escaped by adding a \ in front of it.
System.out.print("\""); // this prints out "
Other characters that needs to be escaped in Java includes: ', ", \.
Print an Owl
Let’s meet 🐥 Patrick’s first friend, the owl Minerva 🦉!
Use what you just learn and recreate this owl below using just 4 lines of code! (Art credit: asciiart.eu/animals/birds-land)
, ___ / ‾ ‾ ‾ ‾ ‾ ‾ ‾ ‾ ‾ ‾ ‾ ‾ ‾ ‾ ‾ ‾ ‾ ‾ \
`\/{o,o} < Hi, I am Minerva. Patrick's friend! |
/ /) ) \ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ /
/,--"-"-
I got an error!
Main.java:4: error: reached end of file while parsing
If you get an error like this such as, it is posible that you forgot to escape chararcters such as " and \.
Revisit the third tip above to see how to escape characters in a print statement!
Make a Comment
When creating a Java program, we can jot down some notes by adding one line comment using // or multi-line comment using /* and */ (Note: The instructions in the previous activities were written as comments).
Also, adding comments will not affect the program whatsoever. So, you can add any notes with comments throughout your code!
// sample one line comment
/* sample
* multi-line
* comment */