修改 SafeConcurrentHashMap 的错误。

src/main/java/xyz/zhouxy/plusone/commons/base/JRE.java

@@ -0,0 +1,58 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package xyz.zhouxy.plusone.commons.base;
+
+import org.apache.commons.lang3.StringUtils;
+import org.apache.commons.lang3.reflect.MethodUtils;
+
+/**
+ * JRE version
+ */
+public class JRE {
+
+    private static final int JAVA_8 = 8;
+
+    public static final int CURRENT_VERSION = getJre();
+
+    public static boolean isJava8() {
+        return CURRENT_VERSION == JAVA_8;
+    }
+
+    private static int getJre() {
+        String version = System.getProperty("java.version");
+        boolean isBlank = StringUtils.isBlank(version);
+        if (!isBlank && version.startsWith("1.8")) {
+            return JAVA_8;
+        }
+        // if JRE version is 9 or above, we can get version from
+        // java.lang.Runtime.version()
+        try {
+            Object javaRunTimeVersion = MethodUtils.invokeMethod(Runtime.getRuntime(), "version");
+            return (int) MethodUtils.invokeMethod(javaRunTimeVersion, "major");
+        } catch (Exception e) {
+            // Can't determine current JRE version (maybe java.version is null),
+            // assuming that JRE version is 8.
+        }
+        // default java 8
+        return JAVA_8;
+    }
+
+    private JRE() {
+        throw new IllegalStateException("Utility class");
+    }
+}