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Java example source code file (MultiReader.java)

This example Java source code file (MultiReader.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

annotation, charsource, gwtincompatible, ioexception, iterator, multireader, override, reader, util

The MultiReader.java Java example source code

/*
 * Copyright (C) 2008 The Guava Authors
 *
 * Licensed 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 com.google.common.io;

import com.google.common.annotations.GwtIncompatible;
import com.google.common.base.Preconditions;

import java.io.IOException;
import java.io.Reader;
import java.util.Iterator;

import javax.annotation.Nullable;

/**
 * A {@link Reader} that concatenates multiple readers.
 *
 * @author Bin Zhu
 * @since 1.0
 */
@GwtIncompatible
class MultiReader extends Reader {
  private final Iterator<? extends CharSource> it;
  private Reader current;

  MultiReader(Iterator<? extends CharSource> readers) throws IOException {
    this.it = readers;
    advance();
  }

  /**
   * Closes the current reader and opens the next one, if any.
   */
  private void advance() throws IOException {
    close();
    if (it.hasNext()) {
      current = it.next().openStream();
    }
  }

  @Override
  public int read(@Nullable char cbuf[], int off, int len) throws IOException {
    if (current == null) {
      return -1;
    }
    int result = current.read(cbuf, off, len);
    if (result == -1) {
      advance();
      return read(cbuf, off, len);
    }
    return result;
  }

  @Override
  public long skip(long n) throws IOException {
    Preconditions.checkArgument(n >= 0, "n is negative");
    if (n > 0) {
      while (current != null) {
        long result = current.skip(n);
        if (result > 0) {
          return result;
        }
        advance();
      }
    }
    return 0;
  }

  @Override
  public boolean ready() throws IOException {
    return (current != null) && current.ready();
  }

  @Override
  public void close() throws IOException {
    if (current != null) {
      try {
        current.close();
      } finally {
        current = null;
      }
    }
  }
}

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