Refactor answer callback for async DNS query JAVA API

1. refactor AnswerCallback with a generic type
2. support onError in AnswerCallback
3. Fix minor problem reported from API Review

Bug: 124882626
Test: built, flashed, booted
      atest DnsResolverTest DnsPacketTest

Change-Id: I685c9989f8401acb63d2e83f552b2d5b20c41af0

1 files changed, 4 insertions, 13 deletions

diff --git a/core/java/android/net/DnsPacket.java b/core/java/android/net/DnsPacket.java
index 0ac02b1b7b37..83e57e0a047b 100644
--- a/core/java/android/net/DnsPacket.java
+++ b/core/java/android/net/DnsPacket.java
@@ -71,7 +71,7 @@ public abstract class DnsPacket {
     }
 
     /**
-     * It's used both for DNS questions and DNS resource records.
+     * Superclass for DNS questions and DNS resource records.
      *
      * DNS questions (No TTL/RDATA)
      * DNS resource records (With TTL/RDATA)
@@ -96,12 +96,13 @@ public abstract class DnsPacket {
         /**
          * Create a new DnsRecord from a positioned ByteBuffer.
          *
-         * @param ByteBuffer input of record, must be in network byte order
-         *         (which is the default).
          * Reads the passed ByteBuffer from its current position and decodes a DNS record.
          * When this constructor returns, the reading position of the ByteBuffer has been
          * advanced to the end of the DNS header record.
          * This is meant to chain with other methods reading a DNS response in sequence.
+         *
+         * @param ByteBuffer input of record, must be in network byte order
+         *         (which is the default).
          */
         DnsRecord(int recordType, @NonNull ByteBuffer buf)
                 throws BufferUnderflowException, ParseException {
@@ -205,16 +206,6 @@ public abstract class DnsPacket {
     protected final DnsHeader mHeader;
     protected final List<DnsRecord>[] mRecords;
 
-    public static class ParseException extends Exception {
-        public ParseException(String msg) {
-            super(msg);
-        }
-
-        public ParseException(String msg, Throwable cause) {
-            super(msg, cause);
-        }
-    }
-
     protected DnsPacket(@NonNull byte[] data) throws ParseException {
         if (null == data) throw new ParseException("Parse header failed, null input data");
         final ByteBuffer buffer;