refactor SortUtils to MapComparator

src/main/java/com/alibaba/druid/util/MapComparator.java

@@ -0,0 +1,58 @@
+package com.alibaba.druid.util;
+
+import java.text.Collator;
+import java.util.Comparator;
+import java.util.Date;
+import java.util.Map;
+
+/**
+ * @author sandzhang<sandzhangtoo@gmail.com>
+ */
+public class MapComparator<K extends Object, V extends Object> implements Comparator<Map<K, V>> {
+
+    private boolean isDesc;
+    private String  orderByKey;
+
+    public MapComparator(String orderByKey, boolean isDesc) {
+        this.orderByKey = orderByKey;
+        this.isDesc = isDesc;
+    }
+
+    private int compare(Number o1, Number o2) {
+        return (int) (o1.doubleValue() - o2.doubleValue());
+    }
+
+    private int compare(String o1, String o2) {
+        return Collator.getInstance().compare(o1, o2);
+    }
+
+    private int compare(Date o1, Date o2) {
+        return (int) (o1.getTime() - o2.getTime());
+    }
+
+    @Override
+    public int compare(Map<K, V> o1, Map<K, V> o2) {
+        int result = compare_0(o1, o2);
+
+        if (isDesc) result = -result;
+
+        return result;
+    }
+
+    public int compare_0(Map<K, V> o1, Map<K, V> o2) {
+        Object v1 = o1.get(orderByKey);
+        Object v2 = o2.get(orderByKey);
+
+        if (v1 == null && v2 == null) return 0;
+        if (v1 == null) return -1;
+        if (v2 == null) return 1;
+
+        if (v1 instanceof Number) return compare((Number) v1, (Number) v2);
+
+        if (v1 instanceof String) return compare((String) v1, (String) v2);
+
+        if (v1 instanceof Date) return compare((Date) v1, (Date) v2);
+
+        return 0;
+    }
+}