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From asdf2014 <...@git.apache.org>
Subject [GitHub] zookeeper pull request #257: ZOOKEEPER-2784: Add same `sid` config problem c...
Date Sat, 20 May 2017 02:29:49 GMT
Github user asdf2014 commented on a diff in the pull request:

    https://github.com/apache/zookeeper/pull/257#discussion_r117599887
  
    --- Diff: src/java/main/org/apache/zookeeper/server/quorum/QuorumCnxManager.java ---
    @@ -310,8 +311,8 @@ public boolean initiateConnection(Socket sock, Long sid) {
          * possible long value to lose the challenge.
          *
          */
    -    public void receiveConnection(Socket sock) {
    -        Long sid = null, protocolVersion = null;
    +    public void receiveConnection(Socket sock) throws ConfigException {
    +        Long sid, protocolVersion;
    --- End diff --
    
    Yeah, actually it could be a problem. `Long == Long` will call `Long.valueof` method,
and compare the address of Object. And the `Long.valueof` method will create a new `Long`
Object when the value of `Long` Object more than 127. So, it could return the `false`.
    ```java
    /*
    127L == 127L: true
    128L == 128L: false
    128L equals 128L: true
    127 == 127: true
    128 == 128: true
     */
    public static void main(String... args) {
        Long l1 = 127L, l2 = 127L, l3 = 128L, l4 = 128L;
        System.out.println("127L == 127L: " + (l1 == l2));
        System.out.println("128L == 128L: " + (l3 == l4));
        System.out.println("128L equals 128L: " + (l3.equals(l4)));
        long ll1 = 127, ll2 = 127, ll3 = 128, ll4 = 128;
        System.out.println("127 == 127: " + (ll1 == ll2));
        System.out.println("128 == 128: " + (ll3 == ll4));
    }
    ```


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