fix NullPointerException hazard in StringUtils.join(..) method

Signed-off-by: WillardHu <[email protected]>
apolloconfig · Sep 14, 2021 · 58771ba · 58771ba
1 parent 0b5d227
commit 58771ba
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Showing 2 changed files with 4 additions and 2 deletions.
diff --git a/apollo-core/src/main/java/com/ctrip/framework/apollo/core/utils/StringUtils.java b/apollo-core/src/main/java/com/ctrip/framework/apollo/core/utils/StringUtils.java
@@ -355,11 +355,11 @@ public String format(T obj) {
 
   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) {
+    if (collection == null) {
       return null;
     }
+    Iterator<T> iterator = collection.iterator();
     if (!iterator.hasNext()) {
       return EMPTY;
     }

diff --git a/apollo-core/src/test/java/com/ctrip/framework/apollo/core/utils/StringUtilsTest.java b/apollo-core/src/test/java/com/ctrip/framework/apollo/core/utils/StringUtilsTest.java
@@ -72,6 +72,8 @@ public void testIsNumeric() {
   public void testJoin() {
     Assert.assertEquals("", StringUtils.join(new ArrayList(), "1a 2b 3c"));
 
+    Assert.assertNull(StringUtils.join(null, "1a 2b 3c"));
+
     ArrayList collection = new ArrayList();
     collection.add(null);
     Assert.assertEquals("", StringUtils.join(collection, "1a 2b 3c"));