Unable to get the idea

Hi All

I am new in Java and reading one of the java book and stuck on one program, the program is below

Code:

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Forty students were asked to rate the quality of the food in the student cafeteria on a
scale of 1 to 10 (where 1 means awful and 10 means excellent). Place the 40 responses
in an integer array, and summarize the results of the poll.

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Code:

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// Fig. 7.8: StudentPoll.java
2      // Poll analysis program.
3
        public class StudentPoll
5      {
6        public static void main( String args[] )
7        {
8        // array of survey responses
9        int responses[] = { 1, 2, 6, 4, 8, 5, 9, 7, 8, 10, 1, 6, 3, 8, 6,
10    10, 3, 8, 2, 7, 6, 5, 7, 6, 8, 6, 7, 5, 6, 6, 5, 6, 7, 5, 6,
11      4, 8, 6, 8, 10 };
12      int frequency[] = new int[ 11 ]; // array of frequency counters
13
14      // for each answer, select responses element and use that value
15    // as frequency index to determine element to increment
16    for ( int answer = 0; answer < responses.length; answer++ )
17    ++frequency[ responses[ answer ] ];
18
19    System.out.printf( "%s%10s", "Rating", "Frequency" );
20
21    // output each array element's value
22    for ( int rating = 1; rating < frequency.length; rating++ )
23    System.out.printf( "%d%10d", rating, frequency[ rating ] );
24    } // end main
25    } // end class StudentPoll

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Can somebody explain me the line no 17. Thank you in advance

Quote:

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for ( int answer = 0; answer < responses.length; answer++ )

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You need to read the tutorial or your text about how for loops work. This is fairly standard in many computer languages.
Go to this site and Find "for statement" Trail: Learning the Java Language: Table of Contents (The Java™ Tutorials)

Thanks for the reply but i am not talking abount loop statement, I am talking abount the below code after loop statement.

Quote:

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++frequency[ responses[ answer ] ];

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His issue is with this statement:

Code:

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++frequency[ responses[ answer ] ];

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My suggestion is that you split this up into several lines to better understand it.

Code:

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int thisAnswer = responses[answer];
++frequency[thisAnswer];

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Note that

Code:

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++frequency[thisAnswer];

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is the same as

Code:

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frequency[thisAnswer] = frequency[thisAnswer] + 1;

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Dyslexia, or need new glasses.

Thanks for the reply, could you please explain it in more details, actually, I am always afraid from array topic and this time I dont want to compromise it.
If you can provide me an example then I will really appreciate you.

Consider using a debugger such as one that is available from NetBeans or Eclipse (or likely whatever IDE you're using) and step through the code to see what happens to the frequency array at that line as this can tell you a lot.

I am using Eclipse but i dont know how debugger works, will try to see the values in debugger and then let you the exact situation. Thank you very much