e.printStackTrace();
先查看下源码
如图片中1所示,使用的是 PrintStreamOrWriter
public void printStackTrace() { printStackTrace(System.err); } /** * Prints this throwable and its backtrace to the specified print stream. * * @param s {@code PrintStream} to use for output */ public void printStackTrace(PrintStream s) { printStackTrace(new WrappedPrintStream(s)); } private void printStackTrace(PrintStreamOrWriter s) { // Guard against malicious overrides of Throwable.equals by // using a Set with identity equality semantics. Set<Throwable> dejaVu = Collections.newSetFromMap(new IdentityHashMap<Throwable, Boolean>()); dejaVu.add(this); synchronized (s.lock()) { // Print our stack trace s.println(this); StackTraceElement[] trace = getOurStackTrace(); for (StackTraceElement traceElement : trace) s.println("\tat " + traceElement); // Print suppressed exceptions, if any for (Throwable se : getSuppressed()) se.printEnclosedStackTrace(s, trace, SUPPRESSED_CAPTION, "\t", dejaVu); // Print cause, if any Throwable ourCause = getCause(); if (ourCause != null) ourCause.printEnclosedStackTrace(s, trace, CAUSE_CAPTION, "", dejaVu); } }
,而这来源于 PrintStream,而 PrintStream 又继承 FilterOutputStream ,是文件输出流,会肯定会影响内存的变动
ublic class PrintStream extends FilterOutputStream implements Appendable, Closeable { private final boolean autoFlush; private boolean trouble = false; private Formatter formatter; /** * Track both the text- and character-output streams, so that their buffers * can be flushed without flushing the entire stream. */ private BufferedWriter textOut; private OutputStreamWriter charOut; /** * requireNonNull is explicitly declared here so as not to create an extra * dependency on java.util.Objects.requireNonNull. PrintStream is loaded * early during system initialization. */ private static <T> T requireNonNull(T obj, String message) { if (obj == null) throw new NullPointerException(message); return obj; } }
而图片中二所示的lock锁,锁住这个流对象,就是占用住了内存不让进行gc回收,先输出打印,
跟踪s.println(this) 也就是PrintStream的方法,发现是会使用bufferedwriter和outputstream
/** * Prints an Object and then terminate the line. This method calls * at first String.valueOf(x) to get the printed object's string value, * then behaves as * though it invokes <code>{@link #print(String)}</code> and then * <code>{@link #println()}</code>. * * @param x The <code>Object</code> to be printed. */ public void println(Object x) { String s = String.valueOf(x); synchronized (this) { print(s); newLine(); } }
/** * Prints a string. If the argument is <code>null</code> then the string * <code>"null"</code> is printed. Otherwise, the string's characters are * converted into bytes according to the platform's default character * encoding, and these bytes are written in exactly the manner of the * <code>{@link #write(int)}</code> method. * * @param s The <code>String</code> to be printed */ public void print(String s) { if (s == null) { s = "null"; } write(s); }
private void write(String s) { try { synchronized (this) { ensureOpen(); textOut.write(s); textOut.flushBuffer(); charOut.flushBuffer(); if (autoFlush && (s.indexOf('\n') >= 0)) out.flush(); } } catch (InterruptedIOException x) { Thread.currentThread().interrupt(); } catch (IOException x) { trouble = true; } }
后又获取 StackTraceElement ,也就是获取方法调用者的具体信息 的。 循环打印
然后又获取报错的异常数据 Throwable的数组, 循环打印