testCreateHashMap

mybatis-plus-core/src/test/java/com/baomidou/mybatisplus/test/toolkit/CollectionUtilsTest.java

@@ -0,0 +1,68 @@
+package com.baomidou.mybatisplus.test.toolkit;
+
+import com.baomidou.mybatisplus.core.toolkit.CollectionUtils;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+import java.lang.reflect.Field;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * @author nieqiuqiu 2020/7/2
+ */
+class CollectionUtilsTest {
+
+    @Test
+    void testCreateHashMap() throws ReflectiveOperationException {
+        Map<String, String> hashMap = newHashMapWithExpectedSize(4);
+        Assertions.assertEquals(8, getTableSize(hashMap));
+        Assertions.assertEquals(6, getThresholdValue(hashMap));
+
+        hashMap = newHashMapWithExpectedSize(11);
+        Assertions.assertEquals(16, getTableSize(hashMap));
+        Assertions.assertEquals(12, getThresholdValue(hashMap));
+
+        hashMap = newHashMapWithExpectedSize(16);
+        Assertions.assertEquals(32, getTableSize(hashMap));
+        Assertions.assertEquals(24, getThresholdValue(hashMap));
+
+        Map<String, String> map = newHashMap(4);
+        Assertions.assertEquals(4, getTableSize(map));
+        Assertions.assertEquals(3, getThresholdValue(map));
+
+        map = newHashMap(11);
+        Assertions.assertEquals(16, getTableSize(map));
+        Assertions.assertEquals(12, getThresholdValue(map));
+
+        map = newHashMap(16);
+        Assertions.assertEquals(16, getTableSize(map));
+        Assertions.assertEquals(12, getThresholdValue(map));
+    }
+
+    private Map<String, String> newHashMapWithExpectedSize(int size) {
+        Map<String, String> hashMap = CollectionUtils.newHashMapWithExpectedSize(size);
+        hashMap.put("1", "1");
+        return hashMap;
+    }
+
+    private Map<String, String> newHashMap(int size) {
+        Map<String, String> map = new HashMap<>(size);
+        map.put("1", "1");
+        return map;
+    }
+
+    private int getTableSize(Map<String, String> map) throws ReflectiveOperationException {
+        Field field = map.getClass().getDeclaredField("table");
+        field.setAccessible(true);
+        Object[] o = (Object[]) field.get(map);
+        return o.length;
+    }
+
+    private int getThresholdValue(Map<String, String> map) throws ReflectiveOperationException {
+        Field field = map.getClass().getDeclaredField("threshold");
+        field.setAccessible(true);
+        return (int) field.get(map);
+    }
+
+}