Unit 1.3: Expressions and Output

Literals

A literal is the source code representation of a fixed value. Literals can be assigned as a value to a primitive data type.

Task: Using literals to initialize variables.

int year = 2025;          // 2025 is an integer literal
double pi = 3.14159;      // 3.14159 is a double literal
boolean isJavaFun = true; // true is a boolean literal
char capitalC = 'C';      // 'C' is a char literal. 

String Literals

A string literal is a sequence of characters enclosed in double quotes.

Task: Defining a String literal.

String message = "This is a string literal.";

Escape Sequences

Escape sequences are special sequences of characters that can be included in a string. They start with a \ and have a special meaning in Java.

Escape sequences used in this course include:

• Double Quote (\"): Used when you want to include a literal double quote inside a string without ending the string.
  • Example: "She said, \"Hello!\"" → Output: She said, "Hello!"
• Backslash (\\): Used when you want to include a literal backslash. Since the backslash is the escape character, you need to use two of them.
  • Example: "C:\\Users\\Desktop" → Output: C:\Users\Desktop
• Newline (\n): Used to move the cursor to the next line within a single string.
  • Example: "First line\nSecond line" → Output:

    First line
    Second line
    

Task: Using escape sequences in an output statement.

System.out.println("She said, \"Hello!\"\nThis is a new line with a backslash: \\");

Output:

She said, "Hello!"
This is a new line with a backslash: \

The Arithmetic Operators

An arithmetic expression is a combination of numeric values (literals), variables, and operators that results in a single numeric value. We will focus on expressions of type int and double.

Arithmetic operators are used in mathematical expressions in the same way that they are used in algebra. The following table lists the arithmetic operators:

Assume integer variable a = 10 and variable b = 20, then:

Operation Result Types

When performing arithmetic, if at least one operand is a double, the result is a double. Otherwise, if both are integer types (int, byte, short), the result is an int.

Integer Division

Integer division (int / int) truncates (cuts off) the decimal portion of the result.

Task: Observing the truncation effect of integer division.

int result = 10 / 3; // result is 3

Remainder Operator

The remainder operator (%) computes the remainder of a division. It is useful for determining if a number is even or odd.

Task: Using the remainder operator to check for even numbers.

int remainder = 10 % 3; // remainder is 1
boolean isEven = (10 % 2 == 0); // isEven is true

Operator Precedence

Java follows the standard order of operations (PEMDAS). *, /, and % are performed before + and -. Use parentheses () to control the order.

Task: Applying operator precedence rules.

int result = 5 + 2 * 3; // Multiplication first: 5 + 6 = 11

Examples of Precedence and Associativity

When operators have the same precedence (like * and /), Java evaluates them from left to right (this is called associativity).

Division by Zero

Dividing an integer by zero results in an ArithmeticException at run-time.

Task: Identifying code that triggers an ArithmeticException.

int a = 10 / 0;

Values in Other Number Systems

EXCLUSION STATEMENT—Binary, octal, and hexadecimal number systems are outside the scope of the AP Computer Science A course and exam. You can skip the below content as appropriate.

All the examples above used the decimal (base 10) number system for initializing the integer values:

• Decimal: Base 10, whose digits consist of the numbers 0 through 9; this is the standard number system familiar to almost everyone.

However, Java also provides Hexadecimal and Octal number systems, as described below:

• Hexadecimal: Base 16, whose digits consist of the numbers 0 through 9 and the letters A through F. This system is mostly used by programmers and is beyond the scope of this book. You must start with 0x when you want to represent a Hexadecimal number.

• Octal: Base 8, whose digits consist of numbers from 0 to 7. You should start with 0 when you want to assign an Octal number.

• Binary: Base 2, whose digits consist of the numbers 0 and 1 (you can create binary literals in Java SE 7 and later). You start a binary representation number with 0b.

You will use the decimal system in this book. However, if you need to use another number system, the following example shows the correct syntax. The prefix 0x indicates hexadecimal and 0b indicates binary:

The number 11, in decimal

int decVal = 11;

The number 11, in hexadecimal

int hexVal = 0xB;

The number 11, in octal

int octVal = 013;

The number 11, in binary

int binVal = 0b1011;