Delete unused method StringUtils.join(..) (#3983)

apollo-core/src/main/java/com/ctrip/framework/apollo/core/utils/StringUtils.java

@@ -344,44 +344,4 @@ public class StringUtils {
     String format(T obj);
   }
 
-  public static <T> String join(Collection<T> collection, String separator) {
-    return join(collection, separator, new StringFormatter<T>() {
-      @Override
-      public String format(T obj) {
-        return obj.toString();
-      }
-    });
-  }
-
-  public static <T> String join(Collection<T> collection, String separator,
-                                StringFormatter<T> formatter) {
-    Iterator<T> iterator = collection.iterator();
-    // handle null, zero and one elements before building a buffer
-    if (iterator == null) {
-      return null;
-    }
-    if (!iterator.hasNext()) {
-      return EMPTY;
-    }
-    T first = iterator.next();
-    if (!iterator.hasNext()) {
-      return first == null ? "" : formatter.format(first);
-    }
-
-    // two or more elements
-    StringBuilder buf = new StringBuilder(256); // Java default is 16, probably too small
-    if (first != null) {
-      buf.append(formatter.format(first));
-    }
-
-    while (iterator.hasNext()) {
-      buf.append(separator);
-      T obj = iterator.next();
-      if (obj != null) {
-        buf.append(formatter.format(obj));
-      }
-    }
-
-    return buf.toString();
-  }
 }

apollo-core/src/test/java/com/ctrip/framework/apollo/core/utils/StringUtilsTest.java

@@ -68,19 +68,6 @@ public class StringUtilsTest {
     Assert.assertTrue(StringUtils.isNumeric("1"));
   }
 
-  @Test
-  public void testJoin() {
-    Assert.assertEquals("", StringUtils.join(new ArrayList(), "1a 2b 3c"));
-
-    ArrayList collection = new ArrayList();
-    collection.add(null);
-    Assert.assertEquals("", StringUtils.join(collection, "1a 2b 3c"));
-
-    collection = new ArrayList();
-    collection.add(-2_147_483_648);
-    Assert.assertEquals("-2147483648", StringUtils.join(collection, "1a 2b 3c"));
-  }
-
   @Test
   public void testStartsWithIgnoreCase() {
     Assert.assertFalse(StringUtils.startsWithIgnoreCase("A1B2C3", "BAZ"));