remove guava Iterables (#6563)

common/src/main/java/com/alibaba/nacos/common/utils/CollectionUtils.java

@@ -26,6 +26,7 @@ import java.util.Iterator;
 import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Map;
+import java.util.NoSuchElementException;
 import java.util.Set;
 
 /**
@@ -278,4 +279,39 @@ public final class CollectionUtils {
             return new LinkedHashSet(Arrays.asList(elements));
         }
     }
+    
+    /**
+     * return the first element, if the iterator contains multiple elements,
+     * will throw {@code IllegalArgumentException}.
+     * @throws NoSuchElementException if the iterator is empty
+     * @throws IllegalArgumentException if the iterator contains multiple elements.
+     * The state of the iterator is unspecified.
+     */
+    public static <T> T getOnlyElement(Iterable<T> iterable) {
+        if (iterable == null) {
+            throw new IllegalArgumentException("iterable cannot be null.");
+        }
+        Iterator<T> iterator = iterable.iterator();
+        T first = iterator.next();
+        if (!iterator.hasNext()) {
+            return first;
+        }
+        throw new IllegalArgumentException(buildExceptionMessage(iterator, first));
+    }
+    
+    @SuppressWarnings("PMD.UndefineMagicConstantRule")
+    private static <T> String buildExceptionMessage(Iterator<T> iterator, T first) {
+        String msg = "";
+        msg += "expected one element but was: <";
+        msg += first;
+        for (int i = 0; i < 4 && iterator.hasNext(); i++) {
+            msg += ", ";
+            msg += iterator.next();
+        }
+        if (iterator.hasNext()) {
+            msg += ", ...";
+        }
+        msg += '>';
+        return msg;
+    }
 }

common/src/test/java/com/alibaba/nacos/common/remote/client/RpcClientFactoryTest.java

@@ -18,7 +18,7 @@ package com.alibaba.nacos.common.remote.client;
 
 import com.alibaba.nacos.api.exception.NacosException;
 import com.alibaba.nacos.common.remote.ConnectionType;
-import com.google.common.collect.Iterables;
+import com.alibaba.nacos.common.utils.CollectionUtils;
 import org.junit.After;
 import org.junit.Assert;
 import org.junit.BeforeClass;
@@ -84,7 +84,7 @@ public class RpcClientFactoryTest {
         
         RpcClientFactory.destroyClient("notExistClientName");
         
-        Map.Entry<String, RpcClient> element = Iterables.getOnlyElement(RpcClientFactory.getAllClientEntries());
+        Map.Entry<String, RpcClient> element = CollectionUtils.getOnlyElement(RpcClientFactory.getAllClientEntries());
         Assert.assertEquals("testClient", element.getKey());
         Assert.assertEquals(rpcClient, element.getValue());
         verify(rpcClient, times(0)).shutdown();
@@ -106,7 +106,7 @@ public class RpcClientFactoryTest {
         
         Assert.assertEquals(Collections.singletonMap("labelKey", "labelValue"), client.labels);
         Assert.assertEquals(ConnectionType.GRPC, client.getConnectionType());
-        Assert.assertEquals("testClient", Iterables.getOnlyElement(RpcClientFactory.getAllClientEntries()).getKey());
+        Assert.assertEquals("testClient", CollectionUtils.getOnlyElement(RpcClientFactory.getAllClientEntries()).getKey());
     }
     
     @Test
@@ -136,7 +136,7 @@ public class RpcClientFactoryTest {
         
         Assert.assertEquals(Collections.singletonMap("labelKey", "labelValue"), client.labels);
         Assert.assertEquals(ConnectionType.GRPC, client.getConnectionType());
-        Assert.assertEquals("testClient", Iterables.getOnlyElement(RpcClientFactory.getAllClientEntries()).getKey());
+        Assert.assertEquals("testClient", CollectionUtils.getOnlyElement(RpcClientFactory.getAllClientEntries()).getKey());
     }
     
     @Test
@@ -164,4 +164,5 @@ public class RpcClientFactoryTest {
                 Collections.singletonMap("labelKey", "labelValue")
         );
     }
+    
 }

common/src/test/java/com/alibaba/nacos/common/utils/CollectionUtilsTest.java

@@ -23,11 +23,13 @@ import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 import java.util.Enumeration;
 import java.util.Iterator;
 import java.util.HashSet;
 import java.util.LinkedHashSet;
+import java.util.NoSuchElementException;
 import java.util.Set;
 import java.util.Vector;
 import java.util.stream.Collectors;
@@ -335,4 +337,23 @@ public class CollectionUtilsTest {
     public void testSetNullPointerException() {
         CollectionUtils.set(null);
     }
+    
+    @Test(expected = IllegalArgumentException.class)
+    public void testGetOnlyElementIllegalArgumentException() {
+        List<Integer> list = Arrays.asList(1, 2, 3);
+        CollectionUtils.getOnlyElement(list);
+    }
+    
+    @Test(expected = NoSuchElementException.class)
+    public void testGetOnlyElementNoSuchElementException() {
+        List<Object> list = new ArrayList<>();
+        CollectionUtils.getOnlyElement(list);
+    }
+    
+    @Test
+    public void testGetOnly() {
+        List<Integer> list = Arrays.asList(1);
+        int element = CollectionUtils.getOnlyElement(list);
+        Assert.assertEquals(1, element);
+    }
 }