java arrays and loop situation

Question

We received a question on making a program for entering the name of people and their gender(n number) and to store the boys and girls in two separate arrays. I wrote the following code but it does not accept both the name and the gender from the second loop. Why?

import java.io.*;

class arrays
{
    BufferedReader br=new BufferedReader(new InputStreamReader(System.in));

    void main()throws IOException
    {
        String name="";
        System.out.println("enter number of students");
        int n=Integer.parseInt(br.readLine());
        String[] c=new String[n];//5
        String[] b=new String[n];//5
        String[] g=new String[n];//5
        char[] s=new char[n];
        System.out.println("enter the name and gender of "+n+" students");
        int i=0;

        do
        {
            System.out.println("enter the data of "+(i+1)+" student");
            c[i]=br.readLine();
            s[i]=(char)br.read();
            i++;
        }
        while(i<n);

        for(int j=0;j<n;j++)
        {
            if(s[j]=='b'||s[j]=='B')
            {
                System.arraycopy(c,j,b,j,1);
            }
            else if(s[j]=='g'||s[j]=='G')
            {
                System.arraycopy(c,j,g,j,1);
            }
        }
        for(int j=0;j<n;j++)
        {
            System.out.print("boys are:-"+b[j]);
            System.out.println("girls are:-"+g[j]);
        }
    }
}

Proper indentation (or, really, ANY) would help...

Scott Hunter
– Scott Hunter

2014-01-01 14:28:01 +00:00
Commented Jan 1, 2014 at 14:28 — Scott Hunter
– Scott Hunter, Commented Jan 1, 2014 at 14:28
which loop is not iterating second time?

Bennet
– Bennet

2014-01-01 14:28:35 +00:00
Commented Jan 1, 2014 at 14:28 — Bennet
– Bennet, Commented Jan 1, 2014 at 14:28

boxed__l · Accepted Answer · 2014-01-01 14:40:49Z

1

The way input is given is the issue here. Change do-while loop to this:

do {
        System.out.println("enter the data of " + (i + 1) + " student");
        c[i] = br.readLine();
        s[i] = (char) br.read();            
        br.readLine();       // even a br.read(); would work. Used to read newline
        i++;
   } while (i < n);

edited Jan 1, 2014 at 14:40

answered Jan 1, 2014 at 14:33

boxed__l

1,3361 gold badge10 silver badges25 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Roger Lindsjö · Accepted Answer · 2014-01-01 14:52:44Z

Your problem is that when you only do br.read() which behaves differently from readLine(). readLine() reads up to and includes the new-line but removes the new-line from the response. So if you enter "the name<new-line>" "the name" is returned but "<new-line>" is consumed. However, the read() reads just one character and leaves the rest as is, so when you enter "b<new-line>" 'b' is returned while "<new-line>" is left on the input stream. So the next time you come around asking for a name using readLine the input will be parsed up to the the next "" which happens to be the new-line left when entering the gender with no characters before it, thus an empty string is returned.

You can test this using the existing program and the following input:

3
name1
bname2
gname3
b

So you need to make sure the new-line is consumed, perhaps by using a br.readLine()after reading the gender. If you try to consume the new-line by reading an extra character beware that on some systems new-line is actually two characters.

Collectives™ on Stack Overflow

java arrays and loop situation

2 Answers 2

Comments

Comments

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Related