续接：FindBugs Report 解读（一）
四、Correctness关于代码正确性相关方面的
1.BC: Impossible cast (BC_IMPOSSIBLE_CAST)
不可能的类转换，执行时会抛出ClassCastException
2.BC: Impossible downcast (BC_IMPOSSIBLE_DOWNCAST)
父类在向下进行类型转换时抛出ClassCastException
3.BC: Impossible downcast of toArray() result (BC_IMPOSSIBLE_DOWNCAST_OF_TOARRAY)
集合转换为数组元素时发生的类转换错误。
This code is casting the result of calling toArray() on a collection to a type more specific than Object[], as in:
String[] getAsArray(Collection<String> c) {
return (String[]) c.toArray();
}
This
will usually fail by throwing a ClassCastException. The toArray() of
almost all collections return an Object[]. They can't really do anything
else, since the Collection object has no reference to the declared
generic type of the collection.
The correct way to do get an
array of a specific type from a collection is to use c.toArray(new
String[]); or c.toArray(new String[c.size()]); (the latter is slightly
more efficient).
4.BC: instanceof will always return false (BC_IMPOSSIBLE_INSTANCEOF)
采用instaneof方法进行比较时总是返回false。前提是保证它不是由于某些逻辑错误造成的。
5.BIT: Incompatible bit masks (BIT_AND)
错误的使用&位操作符，例如(e & C)
6.BIT: Check to see if ((...) & 0) == 0 (BIT_AND_ZZ)
检查恒等的逻辑错误
7.BIT: Incompatible bit masks (BIT_IOR)
错误的使用|位操作符，例如(e | C)
8.BIT: Check for sign of bitwise operation (BIT_SIGNED_CHECK_HIGH_BIT)
检查逻辑运算符操作返回的标识。例如((event.detail & SWT.SELECTED) > 0)，建议采用!=0代替>0
9.BOA: Class overrides a method implemented in super class Adapter wrongly (BOA_BADLY_OVERRIDDEN_ADAPTER)
子类错误的覆写父类中用于适配监听其他事件的方法，从而导致当触发条件发生时不能被监听者调用
10.Bx: Primitive value is unboxed and coerced for ternary operator (BX_UNBOXED_AND_COERCED_FOR_TERNARY_OPERATOR)
在三元运算符操作时如果没有对值进行封装或者类型转换。例如：b ? e1 : e2
11.DLS: Dead store of class literal (DLS_DEAD_STORE_OF_CLASS_LITERAL)
以类的字面名称方式为一个字段赋值后再也没有去使用它，在1.4jdk中它会自动调用静态的初始化方法，而在jdk1.5中却不会去执行。
12.DLS: Overwritten increment (DLS_OVERWRITTEN_INCREMENT)
覆写增量增加错误i = i++
13.DMI: Bad constant value for month (DMI_BAD_MONTH)
hashNext方法调用next方法。
14.DMI: Collections should not contain themselves (DMI_COLLECTIONS_SHOULD_NOT_CONTAIN_THEMSELVES)
集合没有包含他们自己本身。
15.DMI: Invocation of hashCode on an array (DMI_INVOKING_HASHCODE_ON_ARRAY)
数组直接使用hashCode方法来返回哈希码。
int [] a1 = new int[]{1,2,3,4};
System.out.println(a1.hashCode());
System.out.println(java.util.Arrays.hashCode(a1));
16.DMI: Double.longBitsToDouble invoked on an int (DMI_LONG_BITS_TO_DOUBLE_INVOKED_ON_INT)
17.DMI: Vacuous call to collections (DMI_VACUOUS_SELF_COLLECTION_CALL)
集合的调用不能被感知。例如c.containsAll(c)总是返回true，而c.retainAll(c)的返回值不能被感知。
18.Dm:
Can't use reflection to check for presence of annotation without
runtime retention (DMI_ANNOTATION_IS_NOT_VISIBLE_TO_REFLECTION)
Unless
an annotation has itself been annotated with
@Retention(RetentionPolicy.RUNTIME), the annotation can't be observed
using reflection (e.g., by using the isAnnotationPresent method). .
19.Dm: Useless/vacuous call to EasyMock method (DMI_VACUOUS_CALL_TO_EASYMOCK_METHOD)
While
ScheduledThreadPoolExecutor inherits from ThreadPoolExecutor, a few of
the inherited tuning methods are not useful for it. In particular,
because it acts as a fixed-sized pool using corePoolSize threads and an
unbounded queue, adjustments to maximumPoolSize have no useful effect.
20.EC: equals() used to compare array and nonarray (EC_ARRAY_AND_NONARRAY)
数组对象使用equals方法和非数组对象进行比较。即使比较的双方都是数组对象也不应该使用equals方法，而应该比较它们的内容是否相等使用java.util.Arrays.equals(Object[], Object[]);
21.EC: equals(...) used to compare incompatible arrays (EC_INCOMPATIBLE_ARRAY_COMPARE)
使用equls方法去比较类型不相同的数组。例如：String[] and StringBuffer[], or String[] and int[]
22.EC: Call to equals() with null argument (EC_NULL_ARG)
调用equals的对象为null
23.EC: Call to equals() comparing unrelated class and interface (EC_UNRELATED_CLASS_AND_INTERFACE)
使用equals方法比较不相关的类和接口
24.EC: Call to equals() comparing different interface types (EC_UNRELATED_INTERFACES)
调用equals方法比较不同类型的接口
25.EC: Call to equals() comparing different types (EC_UNRELATED_TYPES)
调用equals方法比较不同类型的类
26.EC: Using pointer equality to compare different types (EC_UNRELATED_TYPES_USING_POINTER_EQUALITY)
This
method uses using pointer equality to compare two references that seem
to be of different types. The result of this comparison will always be
false at runtime.
27.Eq: equals method always returns false (EQ_ALWAYS_FALSE)
使用equals方法返回值总是false
28.Eq: equals method always returns true (EQ_ALWAYS_TRUE)
equals方法返回值总是true
29.Eq: equals method compares class names rather than class objects (EQ_COMPARING_CLASS_NAMES)
使用equals方法去比较一个类的实例和类的类型
30.Eq: Covariant equals() method defined for enum (EQ_DONT_DEFINE_EQUALS_FOR_ENUM)
This
class defines an enumeration, and equality on enumerations are defined
using object identity. Defining a covariant equals method for an
enumeration value is exceptionally bad practice, since it would likely
result in having two different enumeration values that compare as equals
using the covariant enum method, and as not equal when compared
normally. Don't do it.
31.Eq: equals() method defined that doesn't override equals(Object) (EQ_OTHER_NO_OBJECT)
类中定义的equals方法时不要覆写equals（Object）方法
32.Eq: equals() method defined that doesn't override Object.equals(Object) (EQ_OTHER_USE_OBJECT)
类中定义的equals方法时不要覆写Object中的equals（Object）方法
33.Eq: equals method overrides equals in superclass and may not be symmetric (EQ_OVERRIDING_EQUALS_NOT_SYMMETRIC)
34.Eq: Covariant equals() method defined, Object.equals(Object) inherited (EQ_SELF_USE_OBJECT)
类中定义了一组equals方法，但是都是继承的java.lang.Object class中的equals(Object)方法
35.FE: Doomed test for equality to NaN (FE_TEST_IF_EQUAL_TO_NOT_A_NUMBER)
This
code checks to see if a floating point value is equal to the special
Not A Number value (e.g., if (x == Double.NaN)). However, because of the
special semantics of NaN, no value is equal to Nan, including NaN.
Thus, x == Double.NaN always evaluates to false. To check to see if a
value contained in x is the special Not A Number value, use
Double.isNaN(x) (or Float.isNaN(x) if x is floating point precision).
36.FS: Format string placeholder incompatible with passed argument (VA_FORMAT_STRING_BAD_ARGUMENT)
错误使用参数类型来格式化字符串
37.FS: The type of a supplied argument doesn't match format specifier (VA_FORMAT_STRING_BAD_CONVERSION)
指定的格式字符串和参数类型不匹配，例如：String.format("%d", "1")
38.FS: MessageFormat supplied where printf style format expected (VA_FORMAT_STRING_EXPECTED_MESSAGE_FORMAT_SUPPLIED)
但用String的format方法时实际调用了ＭｅｓｓａｇｅＦｏｒｍａｔ中干的格式化方法而引起格式化结果出错。
39.FS: More arguments are passed than are actually used in the format string (VA_FORMAT_STRING_EXTRA_ARGUMENTS_PASSED)
使用String的format方法时有非法的参数也经过了格式化操作。
40.FS: Illegal format string (VA_FORMAT_STRING_ILLEGAL)
格式化String对象语句错误
41.FS: Format string references missing argument (VA_FORMAT_STRING_MISSING_ARGUMENT)
String的format操作缺少必要的参数。
42.FS: No previous argument for format string (VA_FORMAT_STRING_NO_PREVIOUS_ARGUMENT)
格式字符串定义错误，例如：formatter.format("%<s %s", "a", "b"); 抛出MissingFormatArgumentException异常
43.GC: No relationship between generic parameter and method argument (GC_UNRELATED_TYPES)
This
call to a generic collection method contains an argument with an
incompatible class from that of the collection's parameter (i.e., the
type of the argument is neither a supertype nor a subtype of the
corresponding generic type argument). Therefore, it is unlikely that the
collection contains any objects that are equal to the method argument
used here. Most likely, the wrong value is being passed to the method.
In
general, instances of two unrelated classes are not equal. For example,
if the Foo and Bar classes are not related by subtyping, then an
instance of Foo should not be equal to an instance of Bar. Among other
issues, doing so will likely result in an equals method that is not
symmetrical. For example, if you define the Foo class so that a Foo can
be equal to a String, your equals method isn't symmetrical since a
String can only be equal to a String.
In rare cases, people do
define nonsymmetrical equals methods and still manage to make their code
work. Although none of the APIs document or guarantee it, it is
typically the case that if you check if a Collection<String>
contains a Foo, the equals method of argument (e.g., the equals method
of the Foo class) used to perform the equality checks.
44.HE: Signature declares use of unhashable class in hashed construct (HE_SIGNATURE_DECLARES_HASHING_OF_UNHASHABLE_CLASS)
A
method, field or class declares a generic signature where a
non-hashable class is used in context where a hashable class is
required. A class that declares an equals method but inherits a
hashCode() method from Object is unhashable, since it doesn't fulfill
the requirement that equal objects have equal hashCodes.
45.HE: Use of class without a hashCode() method in a hashed data structure (HE_USE_OF_UNHASHABLE_CLASS)
A
class defines an equals(Object) method but not a hashCode() method, and
thus doesn't fulfill the requirement that equal objects have equal
hashCodes. An instance of this class is used in a hash data structure,
making the need to fix this problem of highest importance.
46.ICAST: integral value cast to double and then passed to Math.ceil (ICAST_INT_CAST_TO_DOUBLE_PASSED_TO_CEIL)
integral的值转换为double后使用了Math.ceil方法
47.ICAST: int value cast to float and then passed to Math.round (ICAST_INT_CAST_TO_FLOAT_PASSED_TO_ROUND)
int 类型的值转换为float类型之后调用了Math.round方法
48.IJU: JUnit assertion in run method will not be noticed by JUnit (IJU_ASSERT_METHOD_INVOKED_FROM_RUN_METHOD)
在JUnit中的断言在run方法中不会被告知
49.IJU: TestCase declares a bad suite method (IJU_BAD_SUITE_METHOD)
在一个JUnit类中声明的一个suite()方法必须声明为
public static junit.framework.Test suite()
或者
public static junit.framework.TestSuite suite()的形式。
50.IL: A collection is added to itself (IL_CONTAINER_ADDED_TO_ITSELF)
集合本身作为add方法的参数，这样会引起内容溢出。
51.IL: An apparent infinite loop (IL_INFINITE_LOOP)
方法的自调用引起的死循环
52.IM: Integer multiply of result of integer remainder (IM_MULTIPLYING_RESULT_OF_IREM)
和整数余数进行乘法运算。例如：i % 60 * 1000 是进行(i % 60) * 1000运算而不是 i % (60 * 1000)
53.INT: Bad comparison of nonnegative value with negative constant (INT_BAD_COMPARISON_WITH_NONNEGATIVE_VALUE)
保证非负数和负数进行比较
54.INT: Bad comparison of signed byte (INT_BAD_COMPARISON_WITH_SIGNED_BYTE)
比较有符合数，要先把有符号数转换为无符合数再进行比较
55.IO: Doomed attempt to append to an object output stream (IO_APPENDING_TO_OBJECT_OUTPUT_STREAM)
宣布试图在对象的输出流处添加元素，如果你希望能够添加进一个对象的输出流中必须保证对象的输出流处于打开状态。
56.IP: A parameter is dead upon entry to a method but overwritten (IP_PARAMETER_IS_DEAD_BUT_OVERWRITTEN)
The
initial value of this parameter is ignored, and the parameter is
overwritten here. This often indicates a mistaken belief that the write
to the parameter will be conveyed back to the caller.
传入参数的值被忽略，但是对传入值进行了修改，并返回给了调用者
57.MF: Class defines field that masks a superclass field (MF_CLASS_MASKS_FIELD)
子类中定义了和父类中同名的字段。在调用时会出错
58.MF: Method defines a variable that obscures a field (MF_METHOD_MASKS_FIELD)
在方法中定义的局部变量和类变量或者父类变量同名，从而引起字段混淆。
59.NP: Null pointer dereference (NP_ALWAYS_NULL)
对象赋为null值后 没有被重新赋值
60.NP: Null pointer dereference in method on exception path (NP_ALWAYS_NULL_EXCEPTION)
A
pointer which is null on an exception path is dereferenced here. This
will lead to a NullPointerException when the code is executed. Note
that because FindBugs currently does not prune infeasible exception
paths, this may be a false warning.
Also note that FindBugs
considers the default case of a switch statement to be an exception
path, since the default case is often infeasible.
空指针引用上调用去除引用方法，将发生空指针异常
61.NP: Method does not check for null argument (NP_ARGUMENT_MIGHT_BE_NULL)
方法没有判断参数是否为空
62.NP: close() invoked on a value that is always null (NP_CLOSING_NULL)
一个为空的对象调用close方法
63.NP: Null value is guaranteed to be dereferenced (NP_GUARANTEED_DEREF)
There
is a statement or branch that if executed guarantees that a value is
null at this point, and that value that is guaranteed to be dereferenced
(except on forward paths involving runtime exceptions).
在正常的null判断分支上，对象去除引用操作是受保护的不允许的
64.NP: Value is null and guaranteed to be dereferenced on exception path (NP_GUARANTEED_DEREF_ON_EXCEPTION_PATH)
There
is a statement or branch on an exception path that if executed
guarantees that a value is null at this point, and that value that is
guaranteed to be dereferenced (except on forward paths involving runtime
exceptions).
65.NP: Method call passes null to a nonnull parameter (NP_NONNULL_PARAM_VIOLATION)
方法中为null的参数没有被重新赋值
void test(){
String ss = null;
sya(ss);
}
public void sya(String ad){
ad.getBytes();
}
66.NP: Method may return null, but is declared @NonNull (NP_NONNULL_RETURN_VIOLATION)
方法声明了返回值不能为空，但是方法中有可能返回null
67.NP: A known null value is checked to see if it is an instance of a type (NP_NULL_INSTANCEOF)
检查一个为null的值是否是想要的类型对象，而不是由于粗心或者逻辑错误引起的
68.NP: Possible null pointer dereference (NP_NULL_ON_SOME_PATH)
对象可能没有重新赋值
69.NP: Possible null pointer dereference in method on exception path (NP_NULL_ON_SOME_PATH_EXCEPTION)
A
reference value which is null on some exception control path is
dereferenced here. This may lead to a NullPointerException when the
code is executed. Note that because FindBugs currently does not prune
infeasible exception paths, this may be a false warning.
Also note
that FindBugs considers the default case of a switch statement to be an
exception path, since the default case is often infeasible.
在异常null值处理分支调用的方法上，可能存在对象去除引用操作
70.NP: Method call passes null for nonnull parameter (NP_NULL_PARAM_DEREF_ALL_TARGETS_DANGEROUS)
方法参数中声明为nonnull类型的参数为null
void test(){
String ss = null;
sya(ss);
}
public void sya(@nonnull String ad){
ad.getBytes();
}
71.NP: Store of null value into field annotated NonNull (NP_STORE_INTO_NONNULL_FIELD)
为一个已经声明为不能为null值的属性赋值为null。
72.Nm: Class defines equal(Object); should it be equals(Object)? (NM_BAD_EQUAL)
类中定义了一个equal方法但是却不是覆写的Object对象的equals方法
73.Nm: Class defines hashcode(); should it be hashCode()? (NM_LCASE_HASHCODE)
类中定义了一个hashCode方法但是却不是覆写的Object中的hashCode方法
74.Nm: Class defines tostring(); should it be toString()? (NM_LCASE_TOSTRING)
类中定义了一个toString方法但是却不是覆写的Object中的toString方法
75.Nm: Apparent method/constructor confusion (NM_METHOD_CONSTRUCTOR_CONFUSION)
构造方法定义混乱，保证一个标准的构造函数。例如：
SA(){}
void SA(){
}
76.Nm: Very confusing method names (NM_VERY_CONFUSING)
混乱的方法命名，如getName和getname方法同时出现的时候
77.Nm: Method doesn't override method in superclass due to wrong package for parameter (NM_WRONG_PACKAGE)
方法因为取了不同包中的同名的对象而没有正确覆写父类中的同名方法
import alpha.Foo;
public class A {
public int f(Foo x) { return 17; }
}
----
import beta.Foo;
public class B extends A {
public int f(Foo x) { return 42; }
}
78.QBA: Method assigns boolean literal in boolean expression (QBA_QUESTIONABLE_BOOLEAN_ASSIGNMENT)
再if或者while表达式中使用boolean类型的值时应该使用==去判断，而不是采用=操作
79.RC: Suspicious reference comparison (RC_REF_COMPARISON)
比较两个对象值是否相等时应该采用equals方法，而不是==方法
80.RE: Invalid syntax for regular expression (RE_BAD_SYNTAX_FOR_REGULAR_EXPRESSION)
对正则表达式使用了错误的语法，会抛出未经检查的异常，表明正则表达式模式中的语法错误。
81.RE: File.separator used for regular expression (RE_CANT_USE_FILE_SEPARATOR_AS_REGULAR_EXPRESSION)
使用正则表达式使用了错误的文件分隔符，在windows系统中正则表达式不会匹配’\’而应该使用'\\'
82.RV: Random value from 0 to 1 is coerced to the integer 0 (RV_01_TO_INT)
从0到1随机值被强制为整数值0。在强制得到一个整数之前，你可能想得到多个随机值。或使用Random.nextInt（n）的方法。
83.RV: Bad attempt to compute absolute value of signed 32-bit hashcode (RV_ABSOLUTE_VALUE_OF_HASHCODE)
此代码生成一个哈希码，然后计算该哈希码的绝对值。如果哈希码是Integer.MIN_VALUE的，那么结果将是负数（因为Math.abs（Integer.MIN_VALUE的）== Integer.MIN_VALUE的）。
在2^ 32值之外字符串有一个Integer.MIN_VALUE的hashCode包括“polygenelubricants”，“GydZG_”和“，”DESIGNING WORKHOUSES “。
84.RV: Bad attempt to compute absolute value of signed 32-bit random integer (RV_ABSOLUTE_VALUE_OF_RANDOM_INT)
此代码生成一个随机的符号整数，然后计算该随机整数的绝对值。如果随机数生成数绝对值为Integer.MIN_VALUE的，那么结果将是负数（因为Math.abs（Integer.MIN_VALUE的）== Integer.MIN_VALUE的）。
85.RV: Exception created and dropped rather than thrown (RV_EXCEPTION_NOT_THROWN)
此代码创建一个异常（或错误）的对象，但不会用它做任何事情。例如：if (x < 0)
new IllegalArgumentException("x must be nonnegative");
这可能是程序员的意图抛出创建的异常：
if (x < 0)
throw new IllegalArgumentException("x must be nonnegative");
86.RV: Method ignores return value (RV_RETURN_VALUE_IGNORED)
该方法的返回值应该进行检查。这种警告通常出现在调用一个不可变对象的方法，认为它更新了对象的值。例如：String dateString = getHeaderField(name);
dateString.trim();
程序员似乎以为trim（）方法将更新dateString引用的字符串。但由于字符串是不可改变的，trim（）函数返回一个新字符串值，在这里它是被忽略了。该代码应更正：
String dateString = getHeaderField(name);
dateString = dateString.trim();
87.RpC: Repeated conditional tests (RpC_REPEATED_CONDITIONAL_TEST)
该代码包含对同一个条件试验了两次，两边完全一样例如：（如X == 0 | | x == 0）。可能第二次出现是打算判断别的不同条件（如X == 0 | | y== 0）。
88.SA: Double assignment of field (SA_FIELD_DOUBLE_ASSIGNMENT)
方法中的字段包含了双重任务，例如：
int x;
public void foo() {
x = x = 17;
}
这种为变量赋值是无用的，并可能表明一个逻辑错误或拼写错误。
89.SA: Self assignment of field (SA_FIELD_SELF_ASSIGNMENT)
方法中包含自己对自己赋值的字段。例如：
int x;
public void foo() {
x = x;
}
90.SA: Self comparison of field with itself (SA_FIELD_SELF_COMPARISON)
字段自己进行自比较可能表明错误或逻辑错误。
91.SA: Self comparison of value with itself (SA_LOCAL_SELF_COMPARISON)
方法中对一个局部变量自身进行比较运算，并可说明错误或逻辑错误。请确保您是比较正确的事情。
92.SA: Nonsensical self computation involving a variable (e.g., x & x) (SA_LOCAL_SELF_COMPUTATION)
此方法对同一变量执行了荒谬的计算（如x&x或x-x）操作。由于计算的性质，这一行动似乎没有意义，并可能表明错误或逻辑错误。
93.SF: Dead store due to switch statement fall through (SF_DEAD_STORE_DUE_TO_SWITCH_FALLTHROUGH)
在swtich中先前的case值因为swtich执行失败而被覆写，这就像是忘记使用break推出或者没有使用return语句放回先前的值一样。
94.SF: Dead store due to switch statement fall through to throw (SF_DEAD_STORE_DUE_TO_SWITCH_FALLTHROUGH_TO_THROW)
在swtich中因为出现异常而忽略了对case值的保存。
95.SIC: Deadly embrace of non-static inner class and thread local (SIC_THREADLOCAL_DEADLY_EMBRACE)
如果是一个静态内部类。实际上，在内部类和当前线程有死锁的可能。由于内部类不是静态的，它保留了对外部类的引用。如果线程包含对一个内部类实例的引用，那么内外实例的实例都可以被获取，这样就不具备垃圾会回收的资格。
96.SIO: Unnecessary type check done using instanceof operator (SIO_SUPERFLUOUS_INSTANCEOF)
在进行instanceof操作时进行没有必要的类型检查
97.STI: Unneeded use of currentThread() call, to call interrupted() (STI_INTERRUPTED_ON_CURRENTTHREAD)
此方法调用Thread.currentThread（）调用，只需调用interrupted（）方法。由于interrupted（）是一个静态方法， Thread.interrupted（）更简单易用。
98.STI: Static Thread.interrupted() method invoked on thread instance (STI_INTERRUPTED_ON_UNKNOWNTHREAD)
调用不是当前线程对象的Thread.interrupted()方法，由于interrupted（）方法是静态的，interrupted方法将会调用一个和作者原计划不同的对象。
99.Se: Method must be private in order for serialization to work (SE_METHOD_MUST_BE_PRIVATE)
这个类实现了Serializable接口，并定义自定义序列化的方法/反序列化。但由于这种方法不能声明为private，将被序列化/反序列化的API忽略掉。
100.Se: The readResolve method must not be declared as a static method. (SE_READ_RESOLVE_IS_STATIC)
为使readResolve方法得到序列化机制的识别，不能作为一个静态方法来声明。
101.UMAC: Uncallable method defined in anonymous class (UMAC_UNCALLABLE_METHOD_OF_ANONYMOUS_CLASS)
在匿名类中定义了一个既没有覆写超类中方法也不能直接调用的方法。因为在其他类的方法不能直接引用匿名类声明的方法，似乎这种方法不能被调用，这种方法可能只是没有任何作用的代码，但也可能覆写超类中声明。
102.UR: Uninitialized read of field in constructor (UR_UNINIT_READ)
此构造方法中使用了一个尚未赋值的字段或属性。
String a;
public SA() {
String abc = a;
System.out.println(abc);
}
103.UR: Uninitialized read of field method called from constructor of superclass (UR_UNINIT_READ_CALLED_FROM_SUPER_CONSTRUCTOR)
方法被超类的构造函数调用时，在当前类中的字段或属性还没有被初始化。例如：
abstract class A {
int hashCode;
abstract Object getValue();
A() {
hashCode = getValue().hashCode();
}
}
class B extends A {
Object value;
B(Object v) {
this.value = v;
}
Object getValue() {
return value;
}
}
当B是创建时，A的构造函数将在B为value赋值之前触发，然而在A的初始化方法调用getValue方法时value这个变量还没有被初始化。
104.USELESS_STRING: Invocation of toString on an array (DMI_INVOKING_TOSTRING_ON_ANONYMOUS_ARRAY)
该代码调用上匿名数组的toString（）方法，产生的结果形如[@ 16f0472并没有实际的意义。考虑使用Arrays.toString方法来转换成可读的字符串，提供该数组的内容数组。例如：
String[] a = { "a" };
System.out.println(a.toString());
//正确的使用为
System.out.println(Arrays.toString(a));
105.USELESS_STRING: Invocation of toString on an array (DMI_INVOKING_TOSTRING_ON_ARRAY)
该代码调用上数组的toString（）方法，产生的结果形如[@ 16f0472并不能显示数组的真实内容。考虑使用Arrays.toString方法来转换成可读的字符串，提供该数组的内容数组
106.UwF: Field only ever set to null (UWF_NULL_FIELD)
字段的值总是为null值，所有读取该字段的值都为null。检查错误，如果它确实没有用就删除掉。
107.UwF: Unwritten field (UWF_UNWRITTEN_FIELD
此字段是永远不会写入值。所有读取将返回默认值。检查错误（如果它被初始化？），如果它确实没有用就删除掉。
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