Line number in a *.class file, please help, advanced language guys

Question

dear all,
i use c++ to open a *.class file and try to read line number of code in the file, i have 2 questions:
1. i read line number in a method successfully, but i can not understand the meaning of start_pc, following are one of those data, please explain:
s = start_pc,n = line_number
s , n
0 , 123
8 , 125
23 , 126
29 , 127
34 , 129
38 , 130
2. i can not find where the class's line number are, i.e. class start line and class end line, or field's line number.
does these info exist inside a *.class file?
thx for any light

Answer 1

jdb gets line number of fields from class file, not
source file definitely.I'm not really sure how you tested this, but here's my test, and JDB definitely gets its listing from the source file.
First, I created and compiled class Tester:
public class Tester
    public static void main( String[] argv )
    throws Exception
        Tester x = new Tester();
        System.out.println(x.toString());
    int     x;
    int     y;
    private Tester()
        x = 0;
        y = 1;
}Then, I ran this in JDB. Note lines 16 and 17 in the output from "list":
H:\Workspace>jdb Tester
Initializing jdb ...
stop in Tester.mainDeferring breakpoint Tester.main.
It will be set after the class is loaded.
runrun Tester
Set uncaught java.lang.Throwable
Set deferred uncaught java.lang.Throwable
>
VM Started: Set deferred breakpoint Tester.main
Breakpoint hit: "thread=main", Tester.main(), line=12 bci=0
12            Tester x = new Tester();
main[1] list
8    {
9        public static void main( String[] argv )
10        throws Exception
11        {
12 =>         Tester x = new Tester();
13            System.out.println(x.toString());
14        }
15
16        int     x;
17        int     y;
main[1] quit
Tester@b82368Then I edited the source file. Again, look at lines 16 and 17:
H:\Workspace>jdb Tester
Initializing jdb ...
stop in Tester.mainDeferring breakpoint Tester.main.
It will be set after the class is loaded.
runrun Tester
Set uncaught java.lang.Throwable
Set deferred uncaught java.lang.Throwable
>
VM Started: Set deferred breakpoint Tester.main
Breakpoint hit: "thread=main", Tester.main(), line=12 bci=0
12            Tester x = new Tester();
main[1] list
8    {
9        public static void main( String[] argv )
10        throws Exception
11        {
12 =>         Tester x = new Tester();
13            System.out.println(x.toString());
14        }
15
16        int     a;
17        int     b;
main[1]