Add a PrintStream backed by a MultiOutputStream

This goes hand in hand with the previous commit: by overriding stdout
and stderr with MultiPrintStream instances (each backed by a
MultiOutputStream), any interested OutputStreams can add themselves
to the stdout/stderr pipeline without needing to call System.setOut/Err.

This avoids stomping on other interested OutputStreams, and avoids
creating arbitrarily long PrintStream chains which cannot later be
disentangled (since PrintStream has no API for accessing or resetting
its parent after construction).

Author: ctrueden

src/main/java/org/scijava/console/MultiPrintStream.java

@@ -0,0 +1,61 @@
+/*
+ * #%L
+ * SciJava Common shared library for SciJava software.
+ * %%
+ * Copyright (C) 2009 - 2015 Board of Regents of the University of
+ * Wisconsin-Madison, Broad Institute of MIT and Harvard, and Max Planck
+ * Institute of Molecular Cell Biology and Genetics.
+ * %%
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ * 
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ * #L%
+ */
+
+package org.scijava.console;
+
+import java.io.OutputStream;
+import java.io.PrintStream;
+
+/**
+ * A {@link PrintStream} that wraps a {@link MultiOutputStream}.
+ *
+ * @author Curtis Rueden
+ */
+public class MultiPrintStream extends PrintStream {
+
+	public MultiPrintStream(final OutputStream os) {
+		super(multi(os));
+	}
+
+	// -- MultiPrintStream methods --
+
+	public MultiOutputStream getParent() {
+		return (MultiOutputStream) out;
+	}
+
+	// -- Helper methods --
+
+	private static OutputStream multi(final OutputStream os) {
+		if (os instanceof MultiOutputStream) return os;
+		return new MultiOutputStream(os);
+	}
+
+}