fix code to replace join

hutool-core/src/test/java/cn/hutool/core/collection/IterUtilTest.java

@@ -32,6 +32,7 @@ public class IterUtilTest {
 		String join1 = IterUtil.join(list1.iterator(), ":");
 		Assert.assertEquals("1:2:3:4", join1);
 
+		// 包装每个节点
 		ArrayList<String> list2 = CollUtil.newArrayList("1", "2", "3", "4");
 		String join2 = IterUtil.join(list2.iterator(), ":", "\"", "\"");
 		Assert.assertEquals("\"1\":\"2\":\"3\":\"4\"", join2);
@@ -44,6 +45,13 @@ public class IterUtilTest {
 		Assert.assertEquals("1:2:3:4", join);
 	}
 
+	@Test
+	public void joinWithNullTest() {
+		ArrayList<String> list = CollUtil.newArrayList("1", null, "3", "4");
+		String join = IterUtil.join(list.iterator(), ":", String::valueOf);
+		Assert.assertEquals("1:null:3:4", join);
+	}
+
 	@Test
 	public void testToListMap() {
 		Map<String, List<String>> expectedMap = new HashMap<>();

hutool-core/src/test/java/cn/hutool/core/io/ClassPathResourceTest.java

@@ -1,58 +1,58 @@
 package cn.hutool.core.io;
 
+import cn.hutool.core.io.resource.ClassPathResource;
+import cn.hutool.core.util.StrUtil;
+import org.junit.Assert;
+import org.junit.Test;
+
 import java.io.IOException;
 import java.util.Properties;
 
-import org.junit.Assert;
-import org.junit.Test;
-
-import cn.hutool.core.io.resource.ClassPathResource;
-import cn.hutool.core.util.StrUtil;
-
 /**
  * ClassPath资源读取测试
- * @author Looly
  *
+ * @author Looly
  */
 public class ClassPathResourceTest {
-	
+
 	@Test
-	public void readStringTest() throws IOException{
+	public void readStringTest() {
 		ClassPathResource resource = new ClassPathResource("test.properties");
 		String content = resource.readUtf8Str();
 		Assert.assertTrue(StrUtil.isNotEmpty(content));
 	}
-	
+
 	@Test
-	public void readStringTest2() throws IOException{
+	public void readStringTest2() {
+		// 读取classpath根目录测试
 		ClassPathResource resource = new ClassPathResource("/");
 		String content = resource.readUtf8Str();
 		Assert.assertTrue(StrUtil.isNotEmpty(content));
 	}
-	
+
 	@Test
-	public void readTest() throws IOException{
+	public void readTest() throws IOException {
 		ClassPathResource resource = new ClassPathResource("test.properties");
 		Properties properties = new Properties();
 		properties.load(resource.getStream());
-		
+
 		Assert.assertEquals("1", properties.get("a"));
 		Assert.assertEquals("2", properties.get("b"));
 	}
-	
+
 	@Test
-	public void readFromJarTest() throws IOException{
+	public void readFromJarTest() {
 		//测试读取junit的jar包下的LICENSE-junit.txt文件
 		final ClassPathResource resource = new ClassPathResource("LICENSE-junit.txt");
-		
+
 		String result = resource.readUtf8Str();
 		Assert.assertNotNull(result);
-		
+
 		//二次读取测试，用于测试关闭流对再次读取的影响
 		result = resource.readUtf8Str();
 		Assert.assertNotNull(result);
 	}
-	
+
 	@Test
 	public void getAbsTest() {
 		final ClassPathResource resource = new ClassPathResource("LICENSE-junit.txt");

hutool-core/src/test/java/cn/hutool/core/text/StrJoinerTest.java

@@ -0,0 +1,30 @@
+package cn.hutool.core.text;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class StrJoinerTest {
+
+	@Test
+	public void joinIntArrayTest(){
+		int[] a = {1,2,3,4,5};
+		final StrJoiner append = StrJoiner.of(",").append(a);
+		Assert.assertEquals("1,2,3,4,5", append.toString());
+	}
+
+	@Test
+	public void joinEmptyTest(){
+		List<String> list = new ArrayList<>();
+		final StrJoiner append = StrJoiner.of(",").append(list);
+		Assert.assertEquals("", append.toString());
+	}
+
+	@Test
+	public void noJoinTest(){
+		final StrJoiner append = StrJoiner.of(",");
+		Assert.assertEquals("", append.toString());
+	}
+}