Add recaptcha

app/src/main/java/com/hippo/util/HashCodeUtils.java

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+/*
+ * Copyright 2017 Hippo Seven
+ *
+ * Licensed 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 com.hippo.util;
+/*
+ * Created by Hippo on 2017/9/4.
+ */
+
+public class HashCodeUtils {
+
+  private static final int X = 31;
+
+  /**
+   * <pre>{@code
+   * args[0].hashCode()*31^(n-1) + args[1].hashCode()*31^(n-2) + ... + args[n-1].hashCode()
+   * }</pre>
+   * Returns 0 if {@code args == null}.
+   */
+  public static int hashCode(Object... args) {
+    if (args == null) {
+      return 0;
+    }
+    int hash = 0;
+    for (Object o: args) {
+      hash = X * hash + (o != null ? o.hashCode() : 0);
+    }
+    return hash;
+  }
+}