Java tutorial
/* * 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); } } } }