public Builder setOldPeers(int index, java.lang.String value) {
                if (value == null) {
                    throw new NullPointerException();
                }
                ensureOldPeersIsMutable();
                oldPeers_.set(index, value);
                onChanged();
                return this;
            }
<pre>
Don't change field id of `old_peers' in the consideration of backward
compatibility
</pre>

<code>repeated string old_peers = 5;</code>
jraft-core/src/main/java/com/alipay/sofa/jraft/entity/RaftOutter.java