In Java, the execution order is primarily top-to-bottom and left-to-right, but it is governed by specific rules depending on whether you are looking at basic statements, expressions, or class structures.
1. Fundamental Flow
- Sequential Execution: By default, statements are executed one after another in the order they appear in the source code.
- Method Entry: Execution begins at the main method: public static void main(String[] args).
2. Expression Evaluation (Left-to-Right)
While the statements go top-to-bottom, the components within a statement follow these rules:
- Operands: Java evaluates operands from left to right before performing the operation.
- Operator Precedence: Operators with higher precedence (like multiplication *) are evaluated before lower precedence (like addition +).
- Short-Circuiting: For logical operators && and ||, if the first part determines the result, the second part is never evaluated.
3. Control Flow (Non-Linear)
Execution order changes when you use "Jump" or "Decision" statements:
- Selection: if-else and switch skip certain blocks of code based on conditions.
- Iteration: for, while, and do-while loops cause the execution to "jump" back to a previous line until a condition is met.
- Transfer: break, continue, and return immediately redirect the flow to a different part of the program or exit the method.