content: /*
   *  Licensed to the Apache Software Foundation (ASF) under one
   *  or more contributor license agreements.  See the NOTICE file
   *  distributed with this work for additional information
   *  regarding copyright ownership.  The ASF licenses this file
   *  to you under the Apache License, Version 2.0 (the
   *  "License"); you may not use this file except in compliance
   *  with the License.  You may obtain a copy of the License at
   *
   *        http://www.apache.org/licenses/LICENSE-2.0
   *
   *  Unless required by applicable law or agreed to in writing,
   *  software distributed under the License is distributed on an
   *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
   *  KIND, either express or implied.  See the License for the
   *  specific language governing permissions and limitations
   *  under the License.
   */
  package org.apache.causeway.testing.unittestsupport.applib.io;
  
  import java.io.ByteArrayOutputStream;
  import java.io.IOException;
  import java.io.OutputStream;
  import java.io.PrintStream;
  import java.util.concurrent.Callable;
  
  /**
   * @since 2.0 {@index}
   */
  public class NullPrintStream extends PrintStream {
      public NullPrintStream() {
          super(new NullByteArrayOutputStream());
      }
  
      private static class NullByteArrayOutputStream extends ByteArrayOutputStream {
          @Override
          public synchronized void write(int b) {
              // do nothing
          }
  
          @Override
          public synchronized void write(byte[] b, int off, int len) {
              // do nothing
          }
  
          @Override
          public synchronized void writeTo(OutputStream out) throws IOException {
              // do nothing
          }
      }
  
      public static void suppressingStdout(Runnable r)  {
          suppressing(r, true, false);
      }
  
      public static <T> T suppressingStdout(Callable<T> c) throws Exception {
          return suppressing(c, true, false);
      }
  
      public static void suppressingStderr(Runnable r) {
          suppressing(r, false, true);
      }
  
      public static <T> T suppressingStderr(Callable<T> c) throws Exception {
          return suppressing(c, false, true);
      }
  
      public static void suppressing(Runnable r) throws Exception {
          suppressing(r, true, true);
      }
  
      public static <T> T suppressing(Callable<T> c) throws Exception {
          return suppressing(c, true, true);
      }
  
      private static void suppressing(Runnable r, boolean suppressStdout, boolean suppressStderr) {
          PrintStream stdout = System.out;
          PrintStream stderr = System.err;
          try {
              if (suppressStdout) {
                  System.setOut(new NullPrintStream());
              }
              if (suppressStderr) {
                  System.setErr(new NullPrintStream());
              }
              r.run();
          } finally {
              if (suppressStdout) {
                  System.setOut(stdout);
              }
              if (suppressStdout) {
                  System.setErr(stderr);
              }
          }
      }
  
      private static <T> T suppressing(Callable<T> c, boolean suppressStdout, boolean suppressStderr) throws Exception {
          PrintStream stdout = System.out;
          PrintStream stderr = System.err;
          try {
              if (suppressStdout) {
                  System.setOut(new NullPrintStream());
              }
              if (suppressStderr) {
                  System.setErr(new NullPrintStream());
              }
              return c.call();
          } finally {
              if (suppressStdout) {
                  System.setOut(stdout);
              }
              if (suppressStdout) {
                  System.setErr(stderr);
              }
          }
      }
  
  }
  