Change static field WEIGHT_MAP to class level

shardingsphere-features/shardingsphere-readwrite-splitting/shardingsphere-readwrite-splitting-core/src/main/java/org/apache/shardingsphere/readwritesplitting/algorithm/loadbalance/WeightReplicaLoadBalanceAlgorithm.java

@@ -34,7 +34,7 @@ public final class WeightReplicaLoadBalanceAlgorithm implements ReadQueryLoadBal
 
     private static final double ACCURACY_THRESHOLD = 0.0001;
 
-    private static final ConcurrentHashMap<String, double[]> weightMap = new ConcurrentHashMap<>();
+    private final ConcurrentHashMap<String, double[]> weightMap = new ConcurrentHashMap<>();
 
     private Properties props;