Advanced Computer Science 1: Semester 1 Study Guide

This guide summarizes the major topics and concepts from Units 1-4 of the CodeHS Nitro course. Use this to review before the exam!

Unit 1: Primitive Types

Key Concepts:

• Data Types:

  • int - Whole numbers (e.g., 5, -10)

  • double - Decimal numbers (e.g., 3.14, -0.5)

  • boolean - True or false values (true, false)

  • String - A sequence of characters (e.g., "Hello", "CodeHS")

• Variables:

  • Must start with a letter, _, or $ (e.g., myVar, _value).

  • Cannot start with numbers or use reserved keywords like class.

• Type Casting:

  • Example: Convert int to double:

    int x = 5;  
    double y = (double) x; // y is now 5.0  
    

Unit 2: Using Objects

Key Concepts:

• Creating Strings:

  • Example:

    String greeting = "Hello";  
    

• Common String Methods:

  • .length() - Returns the number of characters in the string.

    String word = "CodeHS";  
    System.out.println(word.length()); // Output: 6  
    

  • .toUpperCase() - Converts to uppercase.

    System.out.println("hello".toUpperCase()); // Output: HELLO  
    

  • .charAt(index) - Returns the character at a specific index.

    String s = "Java";  
    System.out.println(s.charAt(0)); // Output: J  
    

Unit 3: Boolean Expressions and if Statements

Key Concepts:

• Comparison Operators:

  • == - Equal to

  • != - Not equal to

  • > - Greater than

  • < - Less than

  • >= - Greater than or equal to

  • <= - Less than or equal to

• Logical Operators:

  • && - AND

  • || - OR

  • ! - NOT

• if Statement Syntax:

  if (condition) {  
      // Code to execute if the condition is true  
  } else {  
      // Code to execute if the condition is false  
  }  
  

Example:

int x = 10;  
if (x > 5) {  
    System.out.println("Greater than 5");  
} else {  
    System.out.println("Less than or equal to 5");  
}  

Unit 4: Iteration

Key Concepts:

for Loop:

• Use when you know how many times to repeat the loop.

  for (int i = 0; i < 5; i++) {  
      System.out.println(i);  
  }  
  // Output: 0 1 2 3 4  
  

while Loop:

• Use when the number of repetitions depends on a condition.

  int count = 0;  
  while (count < 3) {  
      System.out.println(count);  
      count++;  
  }  
  // Output: 0 1 2  
  

Infinite Loops:

• Be careful not to create loops that never stop!

  while (true) {  
      System.out.println("This will run forever!");  
  }  
  

Tips for the Exam

1. Understand Examples: Practice similar problems to those provided in this guide.

2. Memorize Key Syntax: Know how to write if statements, for loops, and method calls.

3. Debugging: Make sure you understand common errors, like mismatched braces or incorrect variable types.

4. Review Practice Questions: Try solving previous exercises from CodeHS.

Practice Problems

1. What is the output of the following code?

   int a = 8;  
   double b = 3.0;  
   System.out.println(a / b);  
   

   a. 2
   b. 2.0
   c. 2.6666666666666665
   d. Error

2. What is the result of true && false?
   a. true
   b. false
   c. Error
   d. 0

3. Write a for loop to print numbers 1 through 5.

Study well, and good luck on the exam! 😊