@@ -28,7 +28,7 @@ P3C-PMD implements 49 rules involved in *Alibaba Java Coding Guidelines*, based
* 2 ``[Mandatory]`` A meaningful thread name is helpful to trace the error information, so assign a name when creating threads or thread pools.
Positive example:
```
```java
public class TimerTaskThread extends Thread {
public TimerTaskThread(){
super.setName("TimerTaskThread"); … }
...
...
@@ -44,7 +44,7 @@ Note: Below are the problems created by usage of Executors for thread pool creat
* 5 ``[Mandatory]`` SimpleDataFormat is unsafe, do not define it as a static variable. If you have to, lock or Apache DateUtils class must be used.
Positive example: Pay attention to thread-safety when using DateUtils. It is recommended to use below:
```
```java
private static final ThreadLocal<DateFormat> df = new ThreadLocal<DateFormat>() {
@Override
protected DateFormat initialValue() {
...
...
@@ -70,7 +70,7 @@ Note: subList of ArrayList is an inner class, which is a view of ArrayList. All
Counter example: Do not use toArray method without arguments. Since the return type is Object[], ClassCastException will be thrown when casting it to a different array type.
Positive example:
```
```java
List<String> list = new ArrayList<String>(2);
list.add("guan");
list.add("bao");
...
...
@@ -81,7 +81,7 @@ Note: When using toArray method with arguments, if input array size is not large
* 4 ``[Mandatory]`` Do not use methods which will modify the list after using Arrays.asList to convert array to list, otherwise methods like add/remove/clear will throw UnsupportedOperationException.
Note: The result of asList is the inner class of Arrays, which does not implement methods to modify itself. Arrays.asList is only a transferred interface, data inside which is stored as an array.
```
```java
String[] str = new String[] { "a", "b" };
List<String> list = Arrays.asList(str);
```
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@@ -90,7 +90,7 @@ Case 2: str[0]= "gujin"; list.get(0) will be modified.
* 5 ``[Mandatory]`` Do not remove or add elements to a collection in a foreach loop. Please use Iterator to remove an item. Iterator object should be synchronized when executing concurrent operations.
Counter example:
```
```java
List<String> a = new ArrayList<String>();
a.add("1");
a.add("2");
...
...
@@ -103,7 +103,7 @@ Counter example:
Note: If you try to replace "1" with "2", you will get an unexpected result.
Positive example:
```
```java
Iterator<String> it = a.iterator();
while (it.hasNext()) {
String temp = it.next();
...
...
@@ -180,7 +180,7 @@ Note: We can call the toString method in a POJO directly to print property value
Counter example:
```
```java
String str = "start";
for(int i=0; i<100; i++) {
str = str + "hello";
...
...
@@ -193,14 +193,14 @@ Note: We can call the toString method in a POJO directly to print property value
* 1 ``[Mandatory]`` In a switch block, each case should be finished by break/return. If not, a note should be included to describe at which case it will stop. Within every switch block, a default statement must be present, even if it is empty.
* 2 ``[Mandatory]`` Braces are used with if, else, for, do and while statements, even if the body contains only a single statement. Avoid using the following example:
```
```java
if (condition) statements;
```
* 3 ``[Recommended]`` Do not use complicated expressions in conditional statements (except for frequently used methods like getXxx/isXxx). Using boolean variables to store results of complicated expressions temporarily will increase the code's readability.
Note: Logic within many if statements are very complicated. Readers need to analyze the final results of the conditional expression to understand the branching logic.
