How to solve “illegal start of expression” in java

 

What is “illegal start of expression”?
"Illegal start of expression" is a compilation error in Java that occurs when the Java compiler encounters a statement or expression that violates the language's syntax rules. This error typically suggests that there is a mistake or inconsistency in the code structure.


Reasons for "illegal start of expression" error:

1.    Missing or misplaced parentheses: The error can occur if parentheses are missing or incorrectly placed in an expression, method call, or control statement.

Solution: Ensure that parentheses are used correctly according to Java syntax rules. Verify that each opening parenthesis has a corresponding closing parenthesis in the correct position.

Example:

int sum = (3 + 4; // Missing closing parenthesis

2.    Incorrect use of operators: This error can occur when operators are used incorrectly or in an unexpected context.

Solution: Review the usage of operators and ensure they are applied correctly according to their intended purpose. Check for missing or misplaced operators, as well as any incorrect combinations.

Example:

int result = 10 *; // Operator used without operands

3.    Misplaced or missing semicolons: The error can arise if a semicolon is missing at the end of a statement or if a semicolon is placed incorrectly within an expression.

Solution: Verify that each statement is terminated with a semicolon, as required by Java syntax. Check for misplaced semicolons within expressions or control structures.

Example:

int count = 0; // Missing semicolon at the end of the statement

4.    Syntax errors within control structures: The error can occur when control structures (if statements, loops, etc.) have incorrect syntax, such as missing or misplaced braces.

Solution: Ensure that control structures are properly formatted with correct placement of opening and closing braces. Verify that each opening brace has a corresponding closing brace in the correct position.

Example:

if (x > 0)  // Missing opening brace

    System.out.println("Positive");

5.    Mismatched quotes or string literals: This error can arise if there is an issue with the usage of quotes or string literals in the code.

Solution: Check that quotes are properly matched and used in pairs. Verify the correct usage of escape characters within string literals.

Example:

String message = "Hello; // Missing closing quote


By addressing these reasons and applying the appropriate solutions, you can resolve the "illegal start of expression" error in Java. It is essential to carefully review the specific error message and the corresponding code line to identify the issue accurately and correct any violations of Java's syntax rules.