Unit 1.3: Expressions and Output

AP Computer Science A

Learning Objectives:

  • 1.3.A: Develop code to generate output
  • 1.3.B: Utilize string literals
  • 1.3.C: Create arithmetic expressions

Output Methods in Java

System.out.print vs System.out.println

System.out.println - displays information and moves cursor to new line

System.out.print - displays information without moving cursor

System.out.print("Hello "); System.out.print("World"); System.out.println("!"); System.out.println("Next line");
Hello World! Next line

Arithmetic Operators

The Five Basic Operators

  • + Addition
  • - Subtraction
  • * Multiplication
  • / Division
  • % Remainder (Modulo)
System.out.println(7 + 3); // 10 System.out.println(7 - 3); // 4 System.out.println(7 * 3); // 21 System.out.println(7 / 3); // 2 (integer division!) System.out.println(7 % 3); // 1 (remainder)

Arithmetic Type Rules

Important Rules

  • Operation with two int values produces int result
  • Operation with at least one double produces double result
// int operations System.out.println(5 + 3); // 8 System.out.println(5 / 2); // 2 // double operations System.out.println(5.0 + 3); // 8.0 System.out.println(5.0 / 2); // 2.5 System.out.println(5 / 2.0); // 2.5
8 2 8.0 2.5 2.5

Integer Division

Important Concept!

When dividing two int values, the result is only the integer portion of the quotient (truncated, not rounded).

System.out.println(7 / 2); // 3 (not 3.5!) System.out.println(10 / 3); // 3 (not 3.33...) System.out.println(1 / 2); // 0 (not 0.5!) // To get decimal result: System.out.println(7.0 / 2); // 3.5 System.out.println(7 / 2.0); // 3.5
3 3 0 3.5 3.5

Operator Precedence

Order of Operations (PEMDAS)

  • Parentheses - highest precedence
  • *, /, % - multiplication, division, remainder
  • +, - - addition, subtraction
  • Left to right - for operators of same precedence
System.out.println(2 + 3 * 4); // 14 (not 20) System.out.println((2 + 3) * 4); // 20 System.out.println(10 / 2 * 3); // 15 (left to right) System.out.println(10 / (2 * 3)); // 1
14 20 15 1

Unit 1.3 Summary

Key Concepts Mastered:

  • Output: System.out.print() vs println()
  • Arithmetic Operators: +, -, *, /, %
  • Type Rules: int operations vs double operations
  • Integer Division: Truncates decimal part
  • Operator Precedence: PEMDAS rules

Ready for Unit 1.4!

You now understand expressions and output in Java!

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