Section: a Compiler's First Pass: Report Unbalanced Symbol Errors. an Application of a Stack

Section: A Compiler's First Pass: Report Unbalanced Symbol errors. An Application of a Stack

Assuming LinkedStack implements OurStack finish the main method below to look for and report all unbalanced symbol errors. Only report on these opener/closer pairs: [],(), and {}. The OurStack interface is listed on the next page. It has the four methods of LinkedStack since LinkedStack implements OurStack 1. Construct an empty stack 2. For each character in the input file if it's an opening symbol push it onto the stack else if it is a closing symbol && the stack is empty report error otherwise pop the stack if symbol is not a closer for pop's value report error 3. At end of file, if the stack is not empty, report an error for every element still on the stack public class BalancedSymbolChecker { public static void main(String[] args) { // Use allText as your java source code. // Change it while testing. String allText = Output from the program to the left: "public class A } \n" + " public static void main(String[args)] \n" public class A } + " System.out PRINTln( Hello ); \n" public static void main(String[args)] + " for( int j = 0; j < 6 j++ ) j++ \n" System.out PRINTln( Hello ); + " doub x = 0.0; \n" for( int j = 0; j < 6 j++ ) j++ + " inTeger j = 0; \n" doub x = 0.0; + " System.out.println(Goodbye]; \n" inTeger j = 0;

+ " } \n" System.out.println(Goodbye]; } + "} \n" } + "[{( \n"; [{(

System.out.println(allText); // Apply the algorithm above to detect errors. // Print the most accurate compile time error messages as possible. // Definitely print the number of errors found.

Possible compile time errors:

Missing opener found by line 1 Mismatched closer on line 2 Mismatched closer on line 7 Missing opener found by line 8 Missing opener found by line 9 Found extra opener ( Found extra opener { Found extra opener [

Error count = 8 import java.util.EmptyStackException; public interface OurStack {

/** * Check if the stack is empty to help avoid popping an empty stack. * @returns true if there are zero elements in this stack. */ public boolean isEmpty();

/** * Put element on "top" of this Stack object. * @param element The element to be added at the top of this stack. */ public void push(E element);

/** * Return reference to the element at the top of this stack. * @returns A reference to the top element. * @throws EmptyStackException if the stack is empty. */ public E peek() throws EmptyStackException;

/** * Remove element at top of stack and return a reference to it. * @returns A reference to the most recently pushed element. * @throws EmptyStackException if the stack is empty. */ public E pop() throws EmptyStackException; }