Question

Write a program that reads a Java source-code file and reports the number of keywords (including null, true, and false) in the file. If a keyword is in a comment or in a string, don’t count it. Test your program to count the keywords in the Welcome.java file:

Please input the Java filename: Welcome.java

The number of keywords in the program is 6

Answer 1

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package numberofkeywords;

/**

*

* @author miracle

*/

//Write a program that reads a Java source-code file and reports the number of keywords

//(including null, true, and false) in the file. If a keyword is in a comment or in a string,

//don’t cnt it.

import java.util.*;

import java.io.*;

public class NumberOfKeywords {

public static void main(String[] args) throws Exception {

Scanner sc = new Scanner(System.in);

System.out.print("Please input the Java file name: ");

String file_name = sc.nextLine();

File file = new File(file_name);

if (file.exists() && file_name.substring(

file_name.lastIndexOf(".")).equals(".java")) {

System.out.println("The number of keywords in the program is " + file_name

+ " is " + no_of_keywords(file));

}

else {

System.out.println("File " + file_name + " not found");

}

}

//reports the number of keywords

//(including null, true, and false) in the file.

public static int no_of_keywords(File file) throws Exception {

// Array of all Java Keywords + ture, false and null

String[] keywordString = {"abstract", "assert", "boolean",

"break", "byte", "case", "catch", "char", "class", "const",

"continue", "default", "do", "double", "else", "enum",

"extends", "for", "final", "finally", "float", "goto",

"if", "implements", "import", "instanceof", "int",

"interface", "long", "native", "new", "package", "private",

"protected", "public", "return", "short", "static",

"strictfp", "super", "switch", "synchronized", "this",

"throw", "throws", "transient", "try", "void", "volatile",

"while", "true", "false", "null"};

Set<String> keywordSet =

new HashSet<>(Arrays.asList(keywordString));

int cnt = 0;

Scanner sc = new Scanner(file);

while (sc.hasNext()) {

String word = sc.next();

//If a keyword is in a comment or in a string,

//don’t cnt it.

if (word.equals("//"))

sc.nextLine();

else if (word.contains("\""))

while (sc.hasNext() && !sc.next().contains("\"")) {}

else if (word.contains("/*"))

while (sc.hasNext() && !sc.next().contains("*/")) {}

else if (keywordSet.contains(word))

cnt++;

}

return cnt;

}

}