for #2331 refactor ShardingDataSourceNames#getRandomDataSourceName

sharding-core/sharding-core-common/src/main/java/org/apache/shardingsphere/core/rule/ShardingDataSourceNames.java

@@ -18,12 +18,12 @@
 package org.apache.shardingsphere.core.rule;
 
 import com.google.common.base.Optional;
+import com.google.common.collect.Lists;
 import lombok.Getter;
 import org.apache.shardingsphere.api.config.masterslave.MasterSlaveRuleConfiguration;
 import org.apache.shardingsphere.api.config.sharding.ShardingRuleConfiguration;
 
 import java.util.Collection;
-import java.util.Iterator;
 import java.util.LinkedHashSet;
 import java.util.Random;
 
@@ -100,12 +100,6 @@ public final class ShardingDataSourceNames {
      * @return random data source name
      */
     public String getRandomDataSourceName(final Collection<String> dataSourceNames) {
-        Random random = new Random();
-        int index = random.nextInt(dataSourceNames.size());
-        Iterator<String> iterator = dataSourceNames.iterator();
-        for (int i = 0; i < index; i++) {
-            iterator.next();
-        }
-        return iterator.next();
+        return Lists.newArrayList(dataSourceNames).get(new Random().nextInt(dataSourceNames.size()));
     }
 }