1+ /*********************************************************************************
2+ * (Match grouping symbols) A Java program contains various pairs of grouping *
3+ * symbols, such as: *
4+ * *
5+ * ■ Parentheses: ( and ) *
6+ * ■ Braces: { and } *
7+ * ■ Brackets: [ and ] *
8+ * *
9+ * Note that the grouping symbols cannot overlap. For example, (a{b)} is illegal. *
10+ * Write a program to check whether a Java source-code file has correct pairs of *
11+ * grouping symbols. Pass the source-code file name as a command-line argument. *
12+ *********************************************************************************/
13+ import java .io .*;
14+ import java .util .*;
15+
16+ public class Exercise_20_11 {
17+ public static void main (String []args )throws IOException {
18+ // Check command-line argument
19+ if (args .length !=1 ) {
20+ System .out .println ("Usage: Java Exercise_20_11 Source-codeFileName" );
21+ System .exit (0 );
22+ }
23+
24+ // Check if file exists
25+ File file =new File (args [0 ]);
26+ if (!file .exists ()) {
27+ System .out .println ("The file " +args [0 ] +" does not exist!" );
28+ System .exit (1 );
29+ }
30+
31+ // Create a stack
32+ Stack <Character >symbols =new Stack <>();
33+
34+ try (// Create an input stream for file
35+ Scanner input =new Scanner (file );
36+ ) {
37+ // Continuously read chars from input
38+ while (input .hasNext ()) {
39+ String line =input .nextLine ();
40+ for (int i =0 ;i <line .length ();i ++) {
41+ char ch =line .charAt (i );
42+ // Push symbols (, {, and [ on to the stack
43+ if (ch =='(' ||ch =='{' ||ch =='[' ) {
44+ symbols .push (ch );
45+ }// Process stack
46+ else if (ch ==')' ||ch =='}' ||ch ==']' ) {
47+ processSymbols (symbols ,ch );
48+ }
49+ }
50+ }
51+ }
52+
53+ System .out .println ("The Java source-code " +
54+ (symbols .isEmpty () ?"has" :"does not have" ) +" correct pairs." );
55+ }
56+
57+ /** Method Matchs grouping symbols */
58+ private static void processSymbols (
59+ Stack <Character >stack ,Character ch ) {
60+ // Remove matching symbols from stack
61+ if ((stack .peek () =='(' &&ch ==')' ) ||
62+ (stack .peek () =='[' &&ch ==']' ) ||
63+ (stack .peek () =='{' &&ch =='}' )) {
64+ stack .pop ();
65+ }
66+ else if ((stack .peek () !='(' &&ch ==')' ) ||
67+ (stack .peek () !='[' &&ch ==']' ) ||
68+ (stack .peek () !='{' &&ch =='}' )) {
69+ System .out .println ("The Java source-code does not have"
70+ +" correct pairs." );
71+ System .exit (1 );
72+ }
73+ }
74+ }
