Java Programming Errors and Syntax Rules

Computers in the room start indexing at 1, but standard programming index 0 is typically used.
Code files are identified by their name, such as main dot Java.
Error messages identify the specific file and the line number where the issue exists (e.g., main dot Java 6 means the error is on line 6).

A compilation error occurs when the code cannot be built into a runnable program.
Binary Operators: These require two inputs (e.g., division requires a numerator and a denominator).
Bad Operand Types: An error occurs when a data type is incompatible with an operation, such as trying to divide an int like $8$ by a string like "John Cena".
Division in Java is an arithmetic operation and requires numerical data types for both inputs.
If a compilation error exists, the code never runs, and no output is produced.

These occur when the code compiles successfully and starts running but encounters a fatal issue during execution.
Infinite Loops: Logic that never terminates, such as a loop that continues "eating pizza" indefinitely.
Stack Overflow: This occurs during recursion when there is no end to the branch or base case, causing the recursion to go on forever.
Division by Zero: Attempting an integer division by $0$ will crash the program at runtime.
Execution Flow: Anything in the code that appears before the runtime error will execute (e.g., printing "hello"), but anything following the error will not occur.

A logic error happens when the code runs to completion without crashing but produces incorrect results.
Example: A program designed to identify triangles that outputs "obtuse" for inputs of $3$ , $4$ , and $5$ (which should be a "right" triangle).
Causes: These can stem from incorrect calculations, improper rounding, or failing to follow the order of operations.

Multiplication: Java requires explicit operators. Writing 4ac in code will be interpreted as a single variable named ac rather than $4 \times a \times c$ . All multiplication must use the * operator.
Parentheses: In mathematical formulas like the quadratic formula, numerators and denominators must be explicitly wrapped in parentheses. For example, dividing by $2a$ requires /(2 * a) to avoid dividing by $2$ and then multiplying the result by $a$ .
Range Logic: The mathematical notation 2 < x < 8 will not compile. It must be split into an explicit "and" statement: 2 < x && x < 8.

Question: What is the difference between public static void and public static double?
Response: If a method is marked as void, it does not return a value. If it is marked as double, it must return a decimal (double) value. Use the specific data type (like int, double, or string) if you want to return a statement or value at the end of the method.