In APCS A, students learn that an algorithm is a step-by-step solution to a problem. A program is how we turn an algorithm into code. The compiler translates Java source code into bytecode so the computer can run it.
In APCS A, variables are named storage locations in memory. Data types tell Java what kind of data can be stored (int, double, boolean, etc.). Choosing the correct data type affects accuracy, memory, and the operations you can perform.
Expressions combine values and operators (example: 3 * 4 + 2). Output is sent to the screen using System.out.print or System.out.println. Order of operations matters in evaluating expressions.
Assignment statements store values in variables using the assignment operator =. Input can come from the user or other sources, but APCS A mainly focuses on reading values and assigning them correctly into variables.
APCS A teaches that casting changes one data type into another. Some conversions are automatic (widening) and some require explicit cast (narrowing). Different data types have fixed size/range and can overflow if values get too large.
APCS A uses compound operators like +=, -=, *=, /= to shorten assignment expressions. Example: x += 5; is the same as x = x + 5;.
APCS A shows that Java has a huge standard library with pre-written classes and methods. We don’t rewrite everything — we use the API documentation to find and use existing tools/classes.
APCS A emphasizes that comments explain code to humans. Comments do not affect code execution. Good comments make programs easier to understand, maintain, and debug.
A method signature includes the method name and its parameter list. The signature determines how a method is called and what kind of arguments it must receive.
Class methods are static. You call them by using the class name, not by creating an object. Example: Math.random().
The Math class contains static methods like sqrt(), pow(), and random(). APCS A uses these constantly in calculations and algorithms.
APCS A teaches that classes are blueprints and objects are real instances created from those blueprints. Different objects created from the same class can hold different values.
We create objects using the new operator. Object references point to location in memory where that object is stored.
Instance methods require an object to call them. Example: str.length() calls the length() method on the String object named str.
The String class contains many useful instance methods like substring(), indexOf(), equals(), and compareTo(). APCS A uses String manipulation to process and transform text data.