add qrcode

hutool-core/src/main/java/cn/hutool/core/date/Month.java

@@ -119,7 +119,7 @@ public enum Month {
 	 * 将 {@link Calendar}月份相关值转换为Month枚举对象<br>
 	 *
 	 * @param calendarMonthIntValue Calendar中关于Month的int值
-	 * @return {@link Month}
+	 * @return Month
 	 * @see Calendar#JANUARY
 	 * @see Calendar#FEBRUARY
 	 * @see Calendar#MARCH

hutool-core/src/main/java/cn/hutool/core/io/CharsetDetector.java

@@ -0,0 +1,110 @@
+package cn.hutool.core.io;
+
+import cn.hutool.core.util.ArrayUtil;
+
+import java.io.BufferedInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.nio.ByteBuffer;
+import java.nio.charset.CharacterCodingException;
+import java.nio.charset.Charset;
+import java.nio.charset.CharsetDecoder;
+import java.nio.charset.UnsupportedCharsetException;
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * 编码探测器
+ *
+ * @author looly
+ * @since 5.4.7
+ */
+public class CharsetDetector {
+
+	/**
+	 * 默认的参与测试的编码
+	 */
+	private static final Charset[] DEFAULT_CHARSETS;
+
+	static {
+		String[] names = {
+				"US-ASCII",
+				"UTF-8",
+				"GBK",
+				"GB2312",
+				"BIG5",
+				"GB18030",
+				"UTF-16BE",
+				"UTF-16LE",
+				"UTF-16",
+				"UNICODE"};
+		final List<Charset> list = new ArrayList<>();
+		for (String name : names) {
+			try {
+				list.add(Charset.forName(name));
+			} catch (UnsupportedCharsetException ignore) {
+				//ignore
+			}
+		}
+		DEFAULT_CHARSETS = list.toArray(new Charset[0]);
+	}
+
+	/**
+	 * 探测编码
+	 *
+	 * @param in       流，使用后关闭此流
+	 * @param charsets 需要测试用的编码，null或空使用默认的编码数组
+	 * @return 编码
+	 */
+	public static Charset detect(InputStream in, Charset... charsets) {
+		if (ArrayUtil.isEmpty(charsets)) {
+			charsets = DEFAULT_CHARSETS;
+		}
+		for (Charset charset : charsets) {
+			charset = detectCharset(in, charset);
+			if (null != charset) {
+				return charset;
+			}
+		}
+		return null;
+	}
+
+	/**
+	 * 判断编码
+	 *
+	 * @param in      流
+	 * @param charset 编码
+	 * @return 编码
+	 */
+	private static Charset detectCharset(InputStream in, Charset charset) {
+		try (BufferedInputStream input = IoUtil.toBuffered(in)) {
+			CharsetDecoder decoder = charset.newDecoder();
+
+			byte[] buffer = new byte[512];
+			while (input.read(buffer) > -1) {
+				if (identify(buffer, decoder)) {
+					return charset;
+				}
+			}
+		} catch (IOException e) {
+			throw new IORuntimeException(e);
+		}
+		return null;
+	}
+
+	/**
+	 * 通过try的方式测试指定bytes是否可以被解码，从而判断是否为指定编码
+	 *
+	 * @param bytes   测试的bytes
+	 * @param decoder 解码器
+	 * @return 是否是指定编码
+	 */
+	private static boolean identify(byte[] bytes, CharsetDecoder decoder) {
+		try {
+			decoder.decode(ByteBuffer.wrap(bytes));
+		} catch (CharacterCodingException e) {
+			return false;
+		}
+		return true;
+	}
+}