diff --git a/src/main/java/git/snippet/heap/Code_DistanceLessK.java b/src/main/java/git/snippet/heap/DistanceLessK.java
similarity index 89%
rename from src/main/java/git/snippet/heap/Code_DistanceLessK.java
rename to src/main/java/git/snippet/heap/DistanceLessK.java
index 81fe98af7204cd3a56afe1122ddf8e9dba7b0550..40b22b7f9c3e3fec3b04a06cbbf7b630faff6df4 100644
--- a/src/main/java/git/snippet/heap/Code_DistanceLessK.java
+++ b/src/main/java/git/snippet/heap/DistanceLessK.java
@@ -7,7 +7,7 @@ import java.util.PriorityQueue;
 // 几乎有序是指，如果把数组排好顺序的话，每个元素移动的距离一定不超过k，并且k相对于数组长度来说是比较小的。
 // 请选择一个合适的排序策略，对这个数组进行排序。(从小到大)
 // tips: 加k个数进堆，然后再加入一个，弹出一个，最后堆里面剩下的继续弹出即可 时间复杂度：O(N*logK)
-public class Code_DistanceLessK {
+public class DistanceLessK {
     public static void sortedArrDistanceLessK(int[] arr, int k) {
         k = Math.min(arr.length - 1, k);
         PriorityQueue<Integer> heap = new PriorityQueue<>();
@@ -20,7 +20,9 @@ public class Code_DistanceLessK {
         for (; i < arr.length; i++) {
             heap.offer(arr[i]);
             // 移动一定不会超过K次
-            arr[index++] = heap.poll();
+            if (!heap.isEmpty()) {
+                arr[index++] = heap.poll();
+            }
         }
         while (!heap.isEmpty()) {
             arr[index++] = heap.poll();
diff --git a/src/test/java/git/snippet/common/Generator.java b/src/test/java/git/snippet/common/Generator.java
index 6dbf2586a8b1ed3f6c84d5501830fff273c3098f..50f1b1a4b7304e0e09788193925696da6498b269 100644
--- a/src/test/java/git/snippet/common/Generator.java
+++ b/src/test/java/git/snippet/common/Generator.java
@@ -1,6 +1,34 @@
 package git.snippet.common;
 
+import java.util.Arrays;
+
 public class Generator {
+    // for test
+    // 几乎有序的数组排序测试
+    public static int[] randomArrayNoMoveMoreK(int maxSize, int maxValue, int K) {
+        int[] arr = new int[(int) ((maxSize + 1) * Math.random())];
+        for (int i = 0; i < arr.length; i++) {
+            arr[i] = (int) ((maxValue + 1) * Math.random()) - (int) (maxValue * Math.random());
+        }
+        // 先排个序
+        Arrays.sort(arr);
+        // 然后开始随意交换，但是保证每个数距离不超过K
+        // swap[i] == true, 表示i位置已经参与过交换
+        // swap[i] == false, 表示i位置没有参与过交换
+        boolean[] isSwap = new boolean[arr.length];
+        for (int i = 0; i < arr.length; i++) {
+            int j = Math.min(i + (int) (Math.random() * (K + 1)), arr.length - 1);
+            if (!isSwap[i] && !isSwap[j]) {
+                isSwap[i] = true;
+                isSwap[j] = true;
+                int tmp = arr[i];
+                arr[i] = arr[j];
+                arr[j] = tmp;
+            }
+        }
+        return arr;
+    }
+
     // for test
     public static int[] generateRandomArray(int maxSize, int maxValue) {
         // Math.random() -> [0,1)
diff --git a/src/test/java/git/snippet/heap/Code_DistanceLessKTest.java b/src/test/java/git/snippet/heap/Code_DistanceLessKTest.java
deleted file mode 100644
index a8e91063a5a4a7334a56b4689a90cdb57c3a59fa..0000000000000000000000000000000000000000
--- a/src/test/java/git/snippet/heap/Code_DistanceLessKTest.java
+++ /dev/null
@@ -1,58 +0,0 @@
-package git.snippet.heap;
-
-import git.snippet.common.Generator;
-import org.junit.jupiter.api.Assertions;
-import org.junit.jupiter.api.DisplayName;
-import org.junit.jupiter.api.Test;
-
-import java.util.Arrays;
-
-import static org.junit.jupiter.api.Assertions.*;
-
-@DisplayName("几乎有序的数组排序测试")
-public class Code_DistanceLessKTest {
-
-    @Test
-    @DisplayName("几乎有序的数组排序测试")
-    public void sortedArrDistanceLessK() {
-        int testTime = 500000;
-        int maxSize = 100;
-        int maxValue = 100;
-        for (int i = 0; i < testTime; i++) {
-            int k = (int) (Math.random() * maxSize) + 1;
-            int[] arr = randomArrayNoMoveMoreK(maxSize, maxValue, k);
-            int[] arr1 = Generator.copyArray(arr);
-            int[] arr2 = Generator.copyArray(arr);
-            Code_DistanceLessK.sortedArrDistanceLessK(arr1, k);
-            Arrays.sort(arr2);
-            Assertions.assertArrayEquals(arr1, arr2);
-        }
-    }
-
-
-    // for test
-    public static int[] randomArrayNoMoveMoreK(int maxSize, int maxValue, int K) {
-        int[] arr = new int[(int) ((maxSize + 1) * Math.random())];
-        for (int i = 0; i < arr.length; i++) {
-            arr[i] = (int) ((maxValue + 1) * Math.random()) - (int) (maxValue * Math.random());
-        }
-        // 先排个序
-        Arrays.sort(arr);
-        // 然后开始随意交换，但是保证每个数距离不超过K
-        // swap[i] == true, 表示i位置已经参与过交换
-        // swap[i] == false, 表示i位置没有参与过交换
-        boolean[] isSwap = new boolean[arr.length];
-        for (int i = 0; i < arr.length; i++) {
-            int j = Math.min(i + (int) (Math.random() * (K + 1)), arr.length - 1);
-            if (!isSwap[i] && !isSwap[j]) {
-                isSwap[i] = true;
-                isSwap[j] = true;
-                int tmp = arr[i];
-                arr[i] = arr[j];
-                arr[j] = tmp;
-            }
-        }
-        return arr;
-    }
-
-}
\ No newline at end of file
diff --git a/src/test/java/git/snippet/heap/DistanceLessKTest.java b/src/test/java/git/snippet/heap/DistanceLessKTest.java
new file mode 100644
index 0000000000000000000000000000000000000000..0281e689a83d3422ba374d7d35dd868ca4554073
--- /dev/null
+++ b/src/test/java/git/snippet/heap/DistanceLessKTest.java
@@ -0,0 +1,29 @@
+package git.snippet.heap;
+
+import git.snippet.common.Generator;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import java.util.Arrays;
+
+@DisplayName("几乎有序的数组排序测试")
+public class DistanceLessKTest {
+
+    @Test
+    @DisplayName("几乎有序的数组排序测试")
+    public void sortedArrDistanceLessK() {
+        int testTime = 500000;
+        int maxSize = 100;
+        int maxValue = 100;
+        for (int i = 0; i < testTime; i++) {
+            int k = (int) (Math.random() * maxSize) + 1;
+            int[] arr = Generator.randomArrayNoMoveMoreK(maxSize, maxValue, k);
+            int[] arr1 = Generator.copyArray(arr);
+            int[] arr2 = Generator.copyArray(arr);
+            DistanceLessK.sortedArrDistanceLessK(arr1, k);
+            Arrays.sort(arr2);
+            Assertions.assertArrayEquals(arr1, arr2);
+        }
+    }
+}
\ No newline at end of file