如何将Java Console输出读入字符串缓冲区

好的，这是一个有趣的问题。似乎不是一种同时解决所有

PrintStream

FilterPrintStream

我确实写了一个丑陋的基于反射的解决方法（我想不要在生产代码中使用它：）

class LoggedPrintStream extends PrintStream {    final StringBuilder buf;    final PrintStream underlying;    LoggedPrintStream(StringBuilder sb, OutputStream os, PrintStream ul) {        super(os);        this.buf = sb;        this.underlying = ul;    }    public static LoggedPrintStream create(PrintStream toLog) {        try { final StringBuilder sb = new StringBuilder(); Field f = FilterOutputStream.class.getDeclaredField("out"); f.setAccessible(true); OutputStream psout = (OutputStream) f.get(toLog); return new LoggedPrintStream(sb, new FilterOutputStream(psout) {     public void write(int b) throws IOException {         super.write(b);         sb.append((char) b);     } }, toLog);        } catch (NoSuchFieldException shouldNotHappen) {        } catch (IllegalArgumentException shouldNotHappen) {        } catch (IllegalAccessException shouldNotHappen) {        }        return null;    }}

…可以像这样使用：

public class Test {    public static void main(String[] args) {        // Create logged PrintStreams        LoggedPrintStream lpsOut = LoggedPrintStream.create(System.out);        LoggedPrintStream lpsErr = LoggedPrintStream.create(System.err);        // Set them to stdout / stderr        System.setOut(lpsOut);        System.setErr(lpsErr);        // Print some stuff        System.out.print("hello ");        System.out.println(5);        System.out.flush();        System.err.println("Some error");        System.err.flush();        // Restore System.out / System.err        System.setOut(lpsOut.underlying);        System.setErr(lpsErr.underlying);        // Print the logged output        System.out.println("----- Log for System.out: -----n" + lpsOut.buf);        System.out.println("----- Log for System.err: -----n" + lpsErr.buf);    }}

结果输出：

hello 5Some error----- Log for System.out: -----hello 5----- Log for System.err: -----Some error

（不过请注意，其中的

out

FilterOutputStream