7 at callers.fully.qualified.className.methodName(FileName.java:74)
8
因而我们就可以通过callers.fully.qualified.className信息来找到改行信息，这个className信息即是传入的fqnOfCategoryClass。
如果当前JDK版本是1.4以上，我们就可以通过JDK提供的一些方法来查找：
1 getStackTraceMethod = Throwable.class.getMethod("getStackTrace",
2 noArgs);
3 Class stackTraceElementClass = Class
4 .forName("java.lang.StackTraceElement");
5 getClassNameMethod = stackTraceElementClass.getMethod(
6 "getClassName", noArgs);
7 getMethodNameMethod = stackTraceElementClass.getMethod(
8 "getMethodName", noArgs);
9 getFileNameMethod = stackTraceElementClass.getMethod("getFileName",
10 noArgs);
11 getLineNumberMethod = stackTraceElementClass.getMethod(
12 "getLineNumber", noArgs);
13
14 Object[] noArgs = null;
15 Object[] elements = (Object[]) getStackTraceMethod.invoke(t,
16 noArgs);
17 String prevClass = NA;
18 for (int i = elements.length - 1; i >= 0; i--) {
19 String thisClass = (String) getClassNameMethod.invoke(
20 elements[i], noArgs);
21 if (fqnOfCallingClass.equals(thisClass)) {
22 int caller = i + 1;
23 if (caller < elements.length) {
24 className = prevClass;
25 methodName = (String) getMethodNameMethod.invoke(
26 elements[caller], noArgs);
27 fileName = (String) getFileNameMethod.invoke(
28 elements[caller], noArgs);
29 if (fileName == null) {
30 fileName = NA;
31 }
32 int line = ((Integer) getLineNumberMethod.invoke(
33 elements[caller], noArgs)).intValue();
34 if (line < 0) {
35 lineNumber = NA;
36 } else {
37 lineNumber = String.valueOf(line);
38 }
39 StringBuffer buf = new StringBuffer();
40 buf.append(className);
41 buf.append(".");
42 buf.append(methodName);
43 buf.append("(");
44 buf.append(fileName);
45 buf.append(":");
46 buf.append(lineNumber);
48 this.fullInfo = buf.toString();
49 }
50 return;
51 }
52 prevClass = thisClass;
53 }
否则，则需要我们通过字符串查找的方式来查找：
1 String s;
2 // Protect against multiple access to sw.
3 synchronized (sw) {
4 t.printStackTrace(pw);
5 s = sw.toString();
6 sw.getBuffer().setLength(0);
7 }
8 int ibegin, iend;
9 ibegin = s.lastIndexOf(fqnOfCallingClass);
10 if (ibegin == -1)
11 return;
12 // See bug 44888.
13 if (ibegin + fqnOfCallingClass.length() < s.length()
14 && s.charAt(ibegin + fqnOfCallingClass.length()) != '.') {
15 int i = s.lastIndexOf(fqnOfCallingClass + ".");
16 if (i != -1) {
17 ibegin = i;
18 }
19 }
20
21 ibegin = s.indexOf(Layout.LINE_SEP, ibegin);
22 if (ibegin == -1)
23 return;
24 ibegin += Layout.LINE_SEP_LEN;
25
26 // determine end of line
27 iend = s.indexOf(Layout.LINE_SEP, ibegin);
28 if (iend == -1)
29 return;
30
31 // VA has a different stack trace format which doesn't
32 // need to skip the inital 'at'
33 if (!inVisualAge) {
34 // back up to first blank character
35 ibegin = s.lastIndexOf("at ", iend);
36 if (ibegin == -1)
37 return;
38 // Add 3 to skip "at ";
39 ibegin += 3;
40 }
41 // everything