Variables

1. Open Variables.java (under app/main/java/_training). What do you think this code does?
2. Run the code and see the result.

• The code starts with "int" myNum and "int" myOtherNum. "int" stands for integer, which is a number without a decimal.
• It then states the names after "int," which in this case are myNum and myOtherNum. The equals sign means it is this variable to something, saying it is equal to a value. This code sets the numbers to 1 and 2.
• After this, it makes one last number, myFinalNum. It sets this number equal to the sum of myNum and myOtherNum. Thinking back on Algebra (ugh), you can substitute 1 for myNum and 2 for myOtherNum in the myFinalNum statement. It will become myFinalNum = 1 + 2.
• The computer then prints the result!

3. Modify the code to include a third number that is multiplied by myFinalNum.

• Hint: The sign for multiplication in Java is *, and Java follows Order of Operations (Parentheses, Multiplication / Division, Addition / Subtraction)
• The solution is found in VariablesSolution.java

Variable Types

String

1. Add String myText = "Hello!"; and String myOtherText = "Again!"; to Variables.java.

• A string represents a "string of characters." In other words, string is text!

2. Add the two strings together into a new variable, myFinalText, and print it out.

• String myFinalText = myText + myOtherText;
• System.out.println(myFinalText);
• Does it work?
• What do you think is happening?
• Try to fix it!

Click for Answer!

When you are adding the two strings together, it adds "Hello!" and "Again!". There isn't a space inbetween, resulting in "Hello!Again!" You can fix it by adding a space after "Hello! " or before " Again!" View the solution if confused.

Float

1. Add float myDecimal = 2.5f; and float mySecondDecimal = 5.0f; to Variables.java.

• Float stands for "Floating-point decimal."
• You must use an f after the number declaration, and it must be a decimal.

2. Divide myDecimal by mySecondDecimal and store it in myLastDecimal, and print the output.

• Hint: To divide in java, use /.
• You should get 0.5, which is 1/2. This is true because 2.5 is half of 5.0.

Doubles

1. Add double myDoubleDecimal = 6.7; and double myOtherDouble = 4.1;

• A double is just a "double-length" float.
  • This means that doubles will be twice as accurate, but also require twice as much computer memory.
• You do not need a suffix for numbers, because doubles are the widely accepted standard for numbers.

2. Divide myDoubleDecimal by myOtherDouble, storing the result in myFinalDouble. Print the final output.

Bool

1. Add the following code to Variables.java and run it.

boolean ateBreakfast = true;
boolean ateLunch = true;
boolean ateDinner = false;

System.out.println(ateBreakfast && ateLunch);
System.out.println(ateLunch && ateDinner);

• A boolean is essentially a yes or no, but instead of yes, we say "true", and instead of no, we say "false".
• The && means "and." Look through the code. It prints out ateBreakfast && ateLunch, or ateBreakfast and ateLunch. We ate both of them (they both are true), so it will say true. Meanwhile, ateLunch is true, but ateDinner is not, so on the second print, we did not eat lunch and eat dinner.
• We will talk more about booleans and logic soon.