Topic 1.3 Notes – Expressions and Output

Generating Output with print and println

Java sends output to the screen using:

• System.out.print(...)
• System.out.println(...)

They both display whatever is inside the parentheses. The only difference is what happens after printing.

• print → stays on the same line
• println → moves to the next line (like pressing Enter)

Look at how the output changes in each case:

Comparing print and println output

In the first example, both words appear on the same line. In the second example, each call moves the cursor down before the next line prints.

Example:

System.out.print("Score: ");
System.out.println(95);

Output:

Score: 95

On quizzes, slow down and trace line by line. If the spacing looks strange, check whether print or println was used.

String Literals and Escape Sequences

A literal is a fixed value written directly in code.

• 10 → int literal
• 3.5 → double literal
• "Hello" → string literal

A string literal:

• Is inside double quotes " "
• Must start and end with quotes
• Cannot spill onto another line unless you use an escape sequence

Escape Sequences

An escape sequence starts with \ and represents a special character.

You need to know:

• \" → prints a double quote
• \\ → prints a backslash
• \n → new line

Example:

System.out.println("She said \"Wow!\"");
System.out.println("Path: C:\\Files\\Docs");
System.out.println("Line1\nLine2");

Common mistake:
Writing "C:\new\folder" accidentally triggers \n as a newline. Always escape backslashes.

Arithmetic Expressions in Java

An arithmetic expression combines:

• Numbers (literals)
• Variables
• Operators

It evaluates to either int or double.

The Five Operators

• + addition
• - subtraction
• * multiplication
• / division
• % remainder

int vs double Rule

This rule explains almost every tricky output question:

• int op int → result is int
• If at least one operand is double → result is double

Example:

System.out.println(5 + 2);      // 7
System.out.println(5 + 2.0);    // 7.0

Special double values like infinity or NaN are outside AP scope, so you don’t need to worry about them.

Division and Remainder Rules

Integer Division

If both numbers are int, Java truncates the decimal.

System.out.println(9 / 4);   // 2
System.out.println(1 / 3);   // 0

It does not round. It simply cuts off the decimal part.

To force decimal division:

System.out.println(9 / 4.0);     // 2.25
System.out.println((double)9 / 4); // 2.25

Division by Zero

• int / 0 → ArithmeticException
• Double division by zero is not tested in AP CSA.

The Remainder Operator %

a % b gives what’s left over after dividing a by b.

System.out.println(14 % 5);   // 4

On the AP exam, assume positive values for remainder problems.

Common uses:

• Even check → num % 2
• Breaking numbers into groups

Operator Precedence and Expression Evaluation

Java follows order of operations.

1. *, /, %
2. +, -
3. Same level → evaluated left to right

This left-to-right rule is tested a lot.

Examples:

System.out.println(3 + 4 * 2);   // 11
System.out.println(12 / 3 * 2);  // 8

Second example:

• 12 / 3 = 4
• 4 * 2 = 8

Parentheses override precedence:

System.out.println((3 + 4) * 2);  // 14

String Concatenation and Expression Output

The + operator has two meanings:

• Numeric addition
• String concatenation

If either side is a string, Java switches to concatenation. Evaluation is left to right.

System.out.println("Total: " + 3 + 2);

Steps:

1. "Total: " + 3 → "Total: 3"
2. "Total: 3" + 2 → "Total: 32"

Compare:

System.out.println(3 + 2 + " total");     // "5 total"
System.out.println("Total: " + (3 + 2));  // "Total: 5"

Once a number becomes part of a string, it stays text.

This shows up constantly in multiple choice. If you get a weird answer like "Total: 32", it’s probably a concatenation order issue.