fix mail bug

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

@@ -25,7 +25,7 @@ public class SystemClock {
 
 	/**
 	 * 构造
-	 * @param period
+	 * @param period 时钟更新间隔，单位毫秒
 	 */
 	private SystemClock(long period) {
 		this.period = period;

hutool-core/src/test/java/cn/hutool/core/codec/Base64Test.java

@@ -23,7 +23,7 @@ public class Base64Test {
 		String decodeStr = Base64.decodeStr(encode);
 		Assert.assertEquals(a, decodeStr);
 	}
-	
+
 	@Test
 	public void encodeAndDecodeTest2() {
 		String a = "a61a5db5a67c01445ca2-HZ20181120172058/pdf/中国电信影像云单体网关Docker版-V1.2.pdf";
@@ -33,6 +33,16 @@ public class Base64Test {
 		String decodeStr = Base64.decodeStr(encode, CharsetUtil.UTF_8);
 		Assert.assertEquals(a, decodeStr);
 	}
+
+	@Test
+	public void encodeAndDecodeTest3() {
+		String a = ":";
+		String encode = Base64.encode(a);
+		Assert.assertEquals("Og==", encode);
+
+		String decodeStr = Base64.decodeStr(encode);
+		Assert.assertEquals(a, decodeStr);
+	}
 	
 	@Test
 	public void urlSafeEncodeAndDecodeTest() {