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Java example source code file (Streams.java)

This example Java source code file (Streams.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

appendablewriter, charsequence, currentwrite, eofexception, ioexception, jsonelement, jsonioexception, jsonsyntaxexception, jsonwriter, numberformatexception, override, streams, unsupportedoperationexception, writer

The Streams.java Java example source code

/*
 * Copyright (C) 2010 Google Inc.
 *
 * 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.gson.internal;

import com.google.gson.JsonElement;
import com.google.gson.JsonIOException;
import com.google.gson.JsonNull;
import com.google.gson.JsonParseException;
import com.google.gson.JsonSyntaxException;
import com.google.gson.internal.bind.TypeAdapters;
import com.google.gson.stream.JsonReader;
import com.google.gson.stream.JsonWriter;
import com.google.gson.stream.MalformedJsonException;
import java.io.EOFException;
import java.io.IOException;
import java.io.Writer;

/**
 * Reads and writes GSON parse trees over streams.
 */
public final class Streams {
  private Streams() {
    throw new UnsupportedOperationException();
  }

  /**
   * Takes a reader in any state and returns the next value as a JsonElement.
   */
  public static JsonElement parse(JsonReader reader) throws JsonParseException {
    boolean isEmpty = true;
    try {
      reader.peek();
      isEmpty = false;
      return TypeAdapters.JSON_ELEMENT.read(reader);
    } catch (EOFException e) {
      /*
       * For compatibility with JSON 1.5 and earlier, we return a JsonNull for
       * empty documents instead of throwing.
       */
      if (isEmpty) {
        return JsonNull.INSTANCE;
      }
      // The stream ended prematurely so it is likely a syntax error.
      throw new JsonSyntaxException(e);
    } catch (MalformedJsonException e) {
      throw new JsonSyntaxException(e);
    } catch (IOException e) {
      throw new JsonIOException(e);
    } catch (NumberFormatException e) {
      throw new JsonSyntaxException(e);
    }
  }

  /**
   * Writes the JSON element to the writer, recursively.
   */
  public static void write(JsonElement element, JsonWriter writer) throws IOException {
    TypeAdapters.JSON_ELEMENT.write(writer, element);
  }

  public static Writer writerForAppendable(Appendable appendable) {
    return appendable instanceof Writer ? (Writer) appendable : new AppendableWriter(appendable);
  }

  /**
   * Adapts an {@link Appendable} so it can be passed anywhere a {@link Writer}
   * is used.
   */
  private static final class AppendableWriter extends Writer {
    private final Appendable appendable;
    private final CurrentWrite currentWrite = new CurrentWrite();

    AppendableWriter(Appendable appendable) {
      this.appendable = appendable;
    }

    @Override public void write(char[] chars, int offset, int length) throws IOException {
      currentWrite.chars = chars;
      appendable.append(currentWrite, offset, offset + length);
    }

    @Override public void write(int i) throws IOException {
      appendable.append((char) i);
    }

    @Override public void flush() {}
    @Override public void close() {}

    /**
     * A mutable char sequence pointing at a single char[].
     */
    static class CurrentWrite implements CharSequence {
      char[] chars;
      public int length() {
        return chars.length;
      }
      public char charAt(int i) {
        return chars[i];
      }
      public CharSequence subSequence(int start, int end) {
        return new String(chars, start, end - start);
      }
    }
  }

}

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