public static PushbackReader getPushBackReader(Reader reader, int pushBackSize) {
		return (reader instanceof PushbackReader) ? (PushbackReader) reader : new PushbackReader(reader, pushBackSize);
	}
public static PushbackReader getPushBackReader ( Reader reader , int pushBackSize ) { return ( reader instanceof PushbackReader ) ? ( PushbackReader ) reader : new PushbackReader ( reader , pushBackSize ) ; }
获得{@link PushbackReader}<br>
如果是{@link PushbackReader}强转返回，否则新建

@param reader 普通Reader
@param pushBackSize 推后的byte数
@return {@link PushbackReader}
@since 3.1.0