Fixed #fixed incorrect use list.remove method. (#10935)

* Fixed #fixed incorrect use list.remove method.

* Fixed add License to test file.

pulsar-client-tools/src/main/java/org/apache/pulsar/admin/cli/CmdNamespaceIsolationPolicy.java

@@ -22,12 +22,13 @@
 import java.util.List;
 import java.util.Map;
 import java.util.function.Supplier;
+import java.util.stream.Collectors;
 
+import org.apache.commons.lang3.StringUtils;
 import org.apache.pulsar.admin.cli.utils.NameValueParameterSplitter;
 import org.apache.pulsar.client.admin.PulsarAdmin;
 import org.apache.pulsar.client.admin.PulsarAdminException;
 import org.apache.pulsar.common.policies.data.AutoFailoverPolicyData;
-import org.apache.pulsar.common.policies.data.AutoFailoverPolicyDataImpl;
 import org.apache.pulsar.common.policies.data.AutoFailoverPolicyType;
 import org.apache.pulsar.common.policies.data.BrokerNamespaceIsolationDataImpl;
 import org.apache.pulsar.common.policies.data.BrokerNamespaceIsolationData;
@@ -152,12 +153,9 @@ void run() throws PulsarAdminException {
     }
 
     private List<String> validateList(List<String> list) {
-        for (int i = 0; i < list.size(); i++) {
-            if (list.get(i).isEmpty()) {
-                list.remove(i);
-            }
-        }
-        return list;
+        return list.stream()
+                .filter(StringUtils::isNotEmpty)
+                .collect(Collectors.toList());
     }
 
     private NamespaceIsolationData createNamespaceIsolationData(List<String> namespaces, List<String> primary,

pulsar-client-tools/src/test/java/org/apache/pulsar/admin/cli/TestCmdNamespaceIsolationPolicy.java

@@ -0,0 +1,51 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.pulsar.admin.cli;
+
+import com.google.common.collect.Lists;
+import org.junit.Test;
+import org.testng.Assert;
+
+import java.lang.reflect.InvocationTargetException;
+import java.util.Arrays;
+import java.util.List;
+
+
+public class TestCmdNamespaceIsolationPolicy {
+    @Test
+    public void testValidateListMethodToReturnNonNullStringList() {
+        List<String> mockList = Lists.newArrayList("", "1", "", "", "1", "2", "3", "4", "", "", "", "1", "");
+        List<String> resultList = Lists.newArrayList("1", "1", "2", "3", "4", "1");
+        CmdNamespaceIsolationPolicy cmdNamespaceIsolationPolicy = new CmdNamespaceIsolationPolicy(() -> null);
+        Class<? extends CmdNamespaceIsolationPolicy> klass = cmdNamespaceIsolationPolicy.getClass();
+        Arrays.stream(klass.getDeclaredMethods())
+                .filter((innerMethod) -> innerMethod.getName().contains("validateList"))
+                .findFirst().ifPresent(innerMethod -> {
+            try {
+                innerMethod.setAccessible(true);
+                List<String> calculatedList = (List<String>) innerMethod.invoke(cmdNamespaceIsolationPolicy, mockList);
+                Assert.assertEquals(calculatedList.size(), resultList.size());
+                for (int i = 0; i < resultList.size(); i++)
+                    Assert.assertEquals(resultList.get(i), calculatedList.get(i));
+            } catch (IllegalAccessException | InvocationTargetException e) {
+                e.printStackTrace();
+            }
+        });
+    }
+}