SHOULD BE A STATIC INNER CLASS

官方介紹：

This class is an inner class, but does not use its embedded reference to the object which created it.This reference makes the instances of the class larger, and may keep the reference to the creator object alive longer than necessary.  If possible, the class should be made static

解釋說明：

若成員類中未訪問外圍類的非靜態成員，為避免額外的空間和時間開銷，建議改用靜態成員類。

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EQUALS METHOD OVERRIDES EQUALS IN SUPERCLASS AND MAY NOT BE SYMMETRIC

官方介紹：

This class defines an equals method that overrides an equals method in a superclass. Both equals methods methods use instanceof in the determination of whether two objects are equal. This is fraught with peril, since it is important that the equals method is symmetrical (in other words, a.equals(b) == b.equals(a)). If B is a subtype of A, and A's equals method checks that the argument is an instanceof A, and B's equals method checks that the argument is an instanceof B, it is quite likely that the equivalence relation defined by these methods is not symmetric。

解釋說明：

子類覆蓋了父類中的equals方法，而兩個類中都是用了instanceof來判斷兩個物件是否相等，這個操作存在風險。equals方法應該具有對稱性（a.equals(b) == b.equals(a)），但是當B是A的子類時，A的equals方法檢查引數是A的例項，B的equals方法檢查引數是B的例項，則這些方法定義的equal關係很可能不是對稱的。

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REPEATED CONDITIONAL TESTS

官方介紹：

The code contains a conditional test is performed twice, one right after the other (e.g., x == 0 || x == 0). Perhaps the second occurrence is intended to be something else (e.g., x == 0 || y == 0)。

解釋說明：

該程式碼包含對同一個條件試驗了兩次，兩邊完全一樣例如：（如X == 0 | | x == 0）。可能第二次出現是打算判斷別的不同條件（如X == 0 | | y== 0）。

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RV_RETURN_VALUE_IGNORED_BAD_PRACTICE

官方介紹：

This method returns a value that is not checked. The return value should be checked since it can indicate an unusual or unexpected function execution. For example, the File.delete() method returns false if the file could not be successfully deleted (rather than throwing an Exception). If you don't check the result, you won't notice if the method invocation signals unexpected behavior by returning an atypical return value。

解釋說明：

沒有檢查方法的返回值，但返回值可以代表異常。

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SE_COMPARATOR_SHOULD_BE_SERIALIZABLE

官方說明：

This class implements the Comparator interface. You should consider whether or not it should also implement the Serializable interface. If a comparator is used to construct an ordered collection such as a TreeMap, then the TreeMap will be serializable only if the comparator is also serializable. As most comparators have little or no state, making them serializable is generally easy and good defensive programming。

解釋說明：

Comparator介面沒有實現Serializable介面

修改方式：

實現Serializable介面

DM_NUMBER_CTOR

官方說明：

Using new Integer(int) is guaranteed to always result in a new object whereas Integer.valueOf(int) allows caching of values to be done by the compiler, class library, or JVM. Using of cached values avoids object allocation and the code will be faster。

解釋說明：

效能 - 方法呼叫低效的數字構造方法;使用靜態valueOf代替

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DM_BOXED_PRIMITIVE_FOR_PARSING

官方說明：

A boxed primitive is created from a String, just to extract the unboxed primitive value. It is more efficient to just call the static parseXXX method。

解釋說明：

裝箱和拆箱的問題，把一個字串裝箱，解析獲取箱子中原始值。更有效率就是使用靜態方法，parseXXX 方法。

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