some small tuning

Author: wangweij

src/java.base/share/classes/sun/security/util/DerInputStream.java

@@ -208,7 +208,11 @@ public DerValue[] getSet(int startLen) throws IOException {
     }
 
     public DerValue[] getSet(int startLen, boolean implicit) throws IOException {
-        return getDerValue().subs((byte)0, startLen);
+        if (implicit) {
+            return getDerValue().subs((byte) 0, startLen);
+        } else {
+            return getSet(startLen);
+        }
     }
 
     public int peekByte() throws IOException {
@@ -239,13 +243,12 @@ static int getLength(InputStream in) throws IOException {
         tmp = lenByte;
         if ((tmp & 0x080) == 0x00) { // short form, 1 byte datum
             value = tmp;
-        } else {                     // long form or indefinite
+        } else {                     // long form
             tmp &= 0x07f;
 
             // tmp > 4 indicates more than 4Gb of data.
-            if (tmp < 0 || tmp > 4) {
-                throw new IOException(mdName + "lengthTag=" + tmp + ", "
-                        + ((tmp < 0) ? "incorrect DER encoding." : "too big."));
+            if (tmp > 4) {
+                throw new IOException(mdName + "lengthTag=" + tmp + ", too big.");
             }
 
             value = 0x0ff & in.read();

src/java.base/share/classes/sun/security/util/DerValue.java

@@ -348,7 +348,7 @@ public DerValue(byte[] encoding) throws IOException {
             length = lenByte;
         } else {                     // long form
             lenByte &= 0x07f;
-            if (lenByte < 0 || lenByte > 4) {
+            if (lenByte > 4) {
                 throw new IOException("Invalid lenByte");
             }
             if (len < 2 + lenByte) {
@@ -455,11 +455,7 @@ public final DerInputStream data() {
     }
 
     /**
-     * Returns the data field inside this class. This method should be
-     * avoided because the data field is mutable but every call always
-     * return the same object. The caller had better directly use the
-     * data field. A better way is to call data() that will always return
-     * a new DerInputStream that points to the beginning of the content.
+     * Returns the data field inside this class directly.
      *
      * Both this method and the {@link #data} field should be avoided.
      * Consider using {@link #data()} instead.
@@ -825,7 +821,7 @@ private Date getTimeInternal(boolean generalized) throws IOException {
          */
 
         int year, month, day, hour, minute, second, millis;
-        String type = null;
+        String type;
         int pos = start;
         int len = end - start;
 
@@ -896,15 +892,9 @@ private Date getTimeInternal(boolean generalized) throws IOException {
                     }
                     pos++;
                     switch (precision) {
-                        case 1:
-                            millis += 100 * thisDigit;
-                            break;
-                        case 2:
-                            millis += 10 * thisDigit;
-                            break;
-                        case 3:
-                            millis += thisDigit;
-                            break;
+                        case 1 -> millis += 100 * thisDigit;
+                        case 2 -> millis += 10 * thisDigit;
+                        case 3 -> millis += thisDigit;
                     }
                 }
                 if (precision == 0) {
@@ -1212,6 +1202,6 @@ DerValue[] subs(byte expectedTag, int startLen) throws IOException {
         while (dis.available() > 0) {
             result.add(dis.getDerValue());
         }
-        return result.toArray(new DerValue[result.size()]);
+        return result.toArray(new DerValue[0]);
     }
 }