public void test(String[] str){
if(str!=null)
this.a = str.clone();
}
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2 ）在bean中定義數(shù)組類型的bug
[參考]http://topic.csdn.net/u/20080115/20/c8893ce0-5546-4762-97bb-9b00d10885cc.html
原代碼：
private String[] name;
public String[] getName() {
return name;
}
public void setName(String[] name) {
this.name = name;
}
bug描述：
[EI] May expose internal representation by returning reference to mutable object [EI_EXPOSE_REP]
解決：
private String[] name;
public String[] getName() {
String[] temp = name;
return temp;
}
public void setName(String[] name) {
String[] temp = name;
this.name = temp;
}
說明：
所有容器類型如ArrayList和數(shù)組類型，如果你都自動(dòng)生成get set，都會(huì)有這個(gè)警告。
這個(gè)警告的主要目的是：一般的get set直接把此對(duì)象中某一容器的引用放到外部，可以隨便更改，違反了封裝的原則，至于那個(gè)temp的方法，由于不是直接對(duì)內(nèi)部容器進(jìn)行操作，故沒有警告，但沒有實(shí)際意義，自己知道即可。
Returning a reference to a mutable object value stored in one of the object's fields exposes the internal representation of the object. If instances are accessed by untrusted code, and unchecked changes to the mutable object would compromise security or other important properties, you will need to do something different. Returning a new copy of the object is better approach in many situations.
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3） 序列化問題
源碼：
private Obj[] obj;
public void getObj(){
Obj[] tep = obj;
return tep;
}
public Obj[] setObj(Obj[] o){
Obj[] tep = o;
this.obj = tep;
}
bug描述：
This Serializable class defines a non-primitive instance field which is neither transient, Serializable, or java.lang.Object, and does not appear to implement the Externalizable interface or the readObject() and writeObject() methods. Objects of this class will not be deserialized correctly if a non-Serializable object is stored in this field.
修改：
public class Obj implements Serializable {
...
}
4 ) new Integer(int) 和 Integer.valueOf(int)
bug描述：
[Bx] Method invokes inefficient Number constructor; use static valueOf instead [DM_NUMBER_CTOR]
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.
說明:
[參考]http://www.cnblogs.com/hyddd/articles/1391318.html
FindBugs推薦使用Integer.ValueOf(int)代替new Integer(int)，因?yàn)檫@樣可以提高性能。如果當(dāng)你的int值介于-128～127時(shí)，Integer.ValueOf(int)的效率比Integer(int)快大約3.5倍。
下面看看JDK的源碼，看看到Integer.ValueOf(int)里面做了什么優(yōu)化：
public static Integer valueOf(int i) {
final int offset = 128;
if (i >= -128 && i <= 127) { // must cache
return IntegerCache.cache[i + offset];
}
return new Integer(i);
}
private static class IntegerCache {
private IntegerCache(){}
static final Integer cache[] = new Integer[-(-128) + 127 + 1];
static {
for(int i = 0; i < cache.length; i++)
cache = new Integer(i - 128);
}
}
從源代碼可以知道，ValueOf對(duì)-128～127這256個(gè)值做了緩存(IntegerCache)，如果int值的范圍是：-128～127，在ValueOf(int)時(shí)，他會(huì)直接返回IntegerCache的緩存給你。
所以你會(huì)看到這樣的一個(gè)現(xiàn)象：
public static void main(String []args) {
Integer a = 100;
Integer b = 100;
System.out.println(a==b);
Integer c = new Integer(100);
Integer d = new Integer(100);
System.out.println(c==d);
}
結(jié)果是：
true
false
因?yàn)椋簀ava在編譯的時(shí)候 Integer a = 100; 被翻譯成-> Integer a = Integer.valueOf(100);，所以a和b得到都是一個(gè)Cache對(duì)象，并且是同一個(gè)！而c和d是新創(chuàng)建的兩個(gè)不同的對(duì)象，所以c自然不等于d。
再看看這段代碼：
public static void main(String args[]) throws Exception{
Integer a = 100;
Integer b = a;
a = a + 1; //或者a++;
System.out.println(a==b);
}
結(jié)果是：false
因?yàn)樵趯?duì)a操作時(shí)(a=a+1或者a++)，a重新創(chuàng)建了一個(gè)對(duì)象，而b對(duì)應(yīng)的還是緩存里的100，所以輸出的結(jié)果為false。
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5) toString() 和 String
源碼：
return a.toString();
bug描述
[Dm] Method invokes toString() method on a String [DM_STRING_TOSTRING]
Calling String.toString() is just a redundant operation. Just use the String.
修改為：
return (String) a;
***************************************************************************
未解決bug
1、
[DMI] Code contains a hard coded reference to an absolute pathname [DMI_HARDCODED_ABSOLUTE_FILENAME]
This code constructs a File object using a hard coded to an absolute pathname (e.g., new File("/home/dannyc/workspace/j2ee/src/share/com/sun/enterprise/deployment");