apache log4j打印日志源码出口

Throwable.class:

public void printStackTrace(PrintStream s) {
synchronized (s) {
s.println(this);
StackTraceElement[] trace = getOurStackTrace();
for (int i=0; i < trace.length; i++)
s.println(" at " + trace[i]);

Throwable ourCause = getCause();
if (ourCause != null)
ourCause.printStackTraceAsCause(s, trace);
}
}

cause:

private void printStackTraceAsCause(PrintStream s,
StackTraceElement[] causedTrace)
{
// assert Thread.holdsLock(s);

// Compute number of frames in common between this and caused
StackTraceElement[] trace = getOurStackTrace();
int m = trace.length-1, n = causedTrace.length-1;
while (m >= 0 && n >=0 && trace[m].equals(causedTrace[n])) {
m--; n--;
}
int framesInCommon = trace.length - 1 - m;

s.println("Caused by: " + this);
for (int i=0; i <= m; i++)
s.println(" at " + trace[i]);
if (framesInCommon != 0)
s.println(" ... " + framesInCommon + " more");

// Recurse if we have a cause
Throwable ourCause = getCause();
if (ourCause != null)
ourCause.printStackTraceAsCause(s, trace);
}