[ISSUE #6228] Add RandomUtils/RandomUtilsTest (#6243)

* [ISSUE #6228] Add RandomUtils/RandomUtilsTest

* [ISSUE #6228] Canonical code

common/src/main/java/com/alibaba/nacos/common/utils/RandomUtils.java

@@ -0,0 +1,81 @@
+/*
+ * Copyright 1999-2018 Alibaba Group Holding Ltd.
+ *
+ * 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.alibaba.nacos.common.utils;
+
+import java.util.Random;
+
+/**
+ * Random utils.
+ *
+ * @author zzq
+ */
+public class RandomUtils {
+    
+    /**
+     * Random Object for random method.
+     */
+    private static final Random RANDOM = new Random();
+    
+    /**
+     * Returns a random long within the specified range.
+     *
+     * @param startInclusive the smallest value that can be returned, must be non-negative
+     * @param endExclusive   the upper bound (not included)
+     * @return the random long
+     * @throws IllegalArgumentException if startInclusive or endExclusive illegal
+     */
+    public static long nextLong(final long startInclusive, final long endExclusive) {
+        checkParameters(startInclusive, endExclusive);
+        long diff = endExclusive - startInclusive;
+        if (diff == 0) {
+            return startInclusive;
+        }
+        return (long) (startInclusive + (diff * RANDOM.nextDouble()));
+    }
+    
+    /**
+     * Returns a random integer within the specified range.
+     *
+     * @param startInclusive lower limit, must be non-negative
+     * @param endExclusive   the upper bound (not included)
+     * @return the random integer
+     * @throws IllegalArgumentException if startInclusive or endExclusive illegal
+     */
+    public static int nextInt(final int startInclusive, final int endExclusive) {
+        checkParameters(startInclusive, endExclusive);
+        int diff = endExclusive - startInclusive;
+        if (diff == 0) {
+            return startInclusive;
+        }
+        return startInclusive + RANDOM.nextInt(diff);
+    }
+    
+    /**
+     * Check input parameters.
+     *
+     * @param startInclusive lower limit, must be non-negative
+     * @param endExclusive   the upper bound (not included)
+     */
+    private static void checkParameters(final long startInclusive, final long endExclusive) {
+        if (endExclusive < startInclusive) {
+            throw new IllegalArgumentException("startInclusive must be less than or equal to the endExclusive.");
+        }
+        if (startInclusive < 0) {
+            throw new IllegalArgumentException("Both parameters must be non-negative");
+        }
+    }
+}

common/src/test/java/com/alibaba/nacos/common/utils/RandomUtilsTest.java

@@ -0,0 +1,39 @@
+/*
+ * Copyright 1999-2018 Alibaba Group Holding Ltd.
+ *
+ * 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.alibaba.nacos.common.utils;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+/**
+ * test RandomUtils.
+ * @author zzq
+ */
+public class RandomUtilsTest {
+    
+    @Test
+    public void nextLong() {
+        final long result = RandomUtils.nextLong(1L, 199L);
+        Assert.assertTrue(result >= 1L && result < 199L);
+    }
+    
+    @Test
+    public void nextInt() {
+        final int result = RandomUtils.nextInt(1, 199);
+        Assert.assertTrue(result >= 1 && result < 199);
+    }
+}