kangjianwei
diff --git a/‎src/java/lang/Enum.java‎
Lines changed: 8 additions & 3 deletions b/‎src/java/lang/Enum.java‎
Lines changed: 8 additions & 3 deletions
diff --git a/‎src/java/lang/Math.java‎
Lines changed: 35 additions & 3 deletions b/‎src/java/lang/Math.java‎
Lines changed: 35 additions & 3 deletions
diff --git a/‎src/java/lang/System.java‎
Lines changed: 8 additions & 6 deletions b/‎src/java/lang/System.java‎
Lines changed: 8 additions & 6 deletions
@@ -176,10 +176,11 @@ public final Class<E> getDeclaringClass() {
      * same enum type.  The natural order implemented by this
      * method is the order in which the constants are declared.
      */
-    // 按自然顺序标胶枚举实例的值
+    // 比较枚举实例的值；声明靠前的枚举，其"值"较小
     public final int compareTo(E o) {
         Enum<?> other = (Enum<?>) o;
         Enum<E> self = this;
+    
         if(self.getClass() != other.getClass() && // optimization
             self.getDeclaringClass() != other.getDeclaringClass()) {
             throw new ClassCastException();
@@ -224,10 +225,14 @@ public final int compareTo(E o) {
      */
     public static <T extends Enum<T>> T valueOf(Class<T> enumType, String name) {
         T result = enumType.enumConstantDirectory().get(name);
-        if(result != null)
+    
+        if(result != null) {
             return result;
-        if(name == null)
+        }
+    
+        if(name == null) {
             throw new NullPointerException("Name is null");
+        }
         throw new IllegalArgumentException("No enum constant " + enumType.getCanonicalName() + "." + name);
     }
 
 
@@ -380,6 +380,15 @@ public static long multiplyHigh(long x, long y) {
         }
     }
 
+    /*
+     * 向下取整除法：
+     *
+     *  11/ 8 =  1.375 ==>  1
+     * -11/ 8 = -1.375 ==> -2
+     *  11/-8 = -1.375 ==> -2
+     * -11/-8 =  1.375 ==>  1
+     */
+    
     /**
      * Returns the largest (closest to positive infinity)
      * {@code int} value that is less than or equal to the algebraic quotient.
@@ -416,7 +425,7 @@ public static long multiplyHigh(long x, long y) {
      * @see #floor(double)
      * @since 1.8
      */
-    // 除法，如果两数符号不同，则向下取整
+    // 向下取整除法
     public static int floorDiv(int x, int y) {
         int r = x / y;
         // if the signs are different and modulo not zero, round down
@@ -453,7 +462,7 @@ public static int floorDiv(int x, int y) {
      * @see #floor(double)
      * @since 9
      */
-    // 除法，如果两数符号不同，则向下取整
+    // 向下取整除法
     public static long floorDiv(long x, int y) {
         return floorDiv(x, (long) y);
     }
@@ -485,7 +494,7 @@ public static long floorDiv(long x, int y) {
      * @see #floor(double)
      * @since 1.8
      */
-    // 除法，如果两数符号不同，则向下取整
+    // 向下取整除法
     public static long floorDiv(long x, long y) {
         long r = x / y;
         // if the signs are different and modulo not zero, round down
@@ -495,6 +504,29 @@ public static long floorDiv(long x, long y) {
         return r;
     }
 
+    /*
+     * 取模运算:
+     *
+     *  11 MOD  8 => 从0开始，顺时针前进11步，得到3
+     * -11 MOD  8 => 从0开始，逆时针前进11步，得到5
+     *
+     *          0
+     *        7   1
+     *      6       2
+     *        5   3
+     *          4
+     *
+     *
+     *  11 MOD -8 => 从0开始，顺时针前进11步，得到-5
+     * -11 MOD -5 => 从0开始，逆时针前进11步，得到-3
+     *
+     *           0
+     *       -1    -7
+     *     -2        -6
+     *       -3    -5
+     *          -4
+     */
+    
     /**
      * Returns the floor modulus of the {@code int} arguments.
      * <p>
 
@@ -88,13 +88,13 @@
  *
  * @since 1.0
  */
-// System工具类
+// 系统工具类
 public final class System {
 
-    // @see #initPhase2()
+    /** @see #initPhase2() */
     static ModuleLayer bootLayer;
 
-    // The security manager for the system. */
+    /** The security manager for the system. */
     // 当前使用的安全管理器，默认为null
     private static volatile SecurityManager security;
 
@@ -264,10 +264,8 @@ public static void setErr(PrintStream err) {
 
     // 为字段System.in关联(初始化)标准输入流
     private static native void setIn0(InputStream in);
-    
     // 为字段System.out关联(初始化)标准输出流
     private static native void setOut0(PrintStream out);
-    
     // 为字段System.err关联(初始化)标准错误流
     private static native void setErr0(PrintStream err);
 
@@ -863,7 +861,11 @@ public static String getenv(String name) {
      *
      * @see java.util.Date
      */
-    // 返回以毫秒为单位的当前时间，其表现为当前时间与GMT时间(格林威治时间)1970年1月1号0时0分0秒所差的毫秒数（具体粒度由底层操作系统决定）
+    /*
+     * 返回当前时间点与新纪元时间点之间的毫秒差值（具体粒度由底层操作系统决定）
+     *
+     * 新纪元时间点：UTC/GMT时间1970年1月1号0时0分0秒
+     */
     @HotSpotIntrinsicCandidate
     public static native long currentTimeMillis();