findbugs检测提示详解

findbugs检测提示详解1、Comparison of String objects using == or !=例，override equals方法时容易犯错if(this.topic != key.getTopic())return false;2、Dead store to newStatusRecord定义局部变量后没有引用3、Invocation of toString on values直接调用数组的toString方法public Query createQuery(String hql, Object values[],Session session){logger.debug(values);logger.debug((newStringBuilder()).append("hql=[").append(hql).append("]").append(((Object)}正确的例子，调用Arrays.toString()和Arrays.deepToString()方法。

import java.util.Arrays;class A{}class B{@Overridepublic String toString() {return "BBBBB";}}public class Test {public static void main(String[] args) {Object [] a = {new Integer(0),new Boolean(true),true,new A(),new B()};Object[][]b ={{new A(),new B()},{new A(),new B()},{new A(),new B()}};System.out.println(Arrays.deepToString(b));}}4、ignores exceptional return value of java.io.File.mkdirs()忽略了返回值，应当含有返回值public void initFolder() {if (!exitDir.isDirectory()) {exitDir.mkdirs();("===Finishing create exit trade image folder!====");}}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.5、不使用new String()定义空的字符串String alarmCodeCond = new String();应当String alarmCodeCond = "";6、invokes inefficient new Short(short) constructor; use Short.valueOf(short) insteadJVM缓存数字常量Short aShort = new Short(12);应当Short aShort = Short.valueOf(12);7、方法命名习惯，首字母小写The method name LaneHandShakeService(Short) doesn't start with a lower case letterMethods should be verbs, in mixed case with the first letter lowercase, with the first letter of each internal word capitalized.8、一个primtive的类型的值经过box后马上unbox Primitive value is boxed then unboxed to perform primitive coercionexitRecord.setEnOperatorId(newLong(transactRecord.getEnoperatorID()).intValue());应当直接强制类型转换exitRecord.setEnOperatorId((int)transactRecord.getEnoperatorID()); 9、Call to equals() comparing different types使用equals()方法比较不同的类，反例StringBuilder builder = new StringBuilder("nihao");String string = "nihao";builder.equals(string);10、Check for oddness that won't work for negative numbers检查奇数的方法：反例if (i % 2 == 1) {//...}The code uses x % 2 == 1 to check to see if a value is odd, but this won't work for negative numbers (e.g., (-5) % 2 == -1). If this code is intending to check for oddness, consider using x & 1 == 1, or x % 2 != 0.11、Load of known null value，null值的不当使用反例：if (devIds == null && devIds.size() == 0) { //... }if (null != tempList || tempList.size() != 0) {//...}if (batchNo == null) {throw new Exception("the No. " + batchNo+ " is not exists!");}12、Method call passes null for nonnull parameter对参数为null的情况没做处理例public void method1() {String ip = null;try {ip = InetAddress.getLocalHost().getHostAddress();} catch (UnknownHostException e) {e.printStackTrace();}long ipCount = countIpAddress(ip); // 可能会传入空引用//... }long countIpAddress(String ip) {long ipNum = 0;String[] ipArray = ip.split("\\.");}修改后：public void method1() {String ip = null;try {ip = InetAddress.getLocalHost().getHostAddress();} catch (UnknownHostException e) {e.printStackTrace();}long ipCount = countIpAddress(ip); // 可能会传入空引用//... }long countIpAddress(String ip) {long ipNum = 0;if (ip == null) {return 0; //或者抛出异常}String[] ipArray = ip.split("\\.");//... }注意：函数入口需要交验入参的合法性。

13、Method concatenates strings using + in a loop在循环里使用字符串连接，效率低，应该使用StringBuilder/StringBuffer例：String writeData = "";for (int i = 0; i < 10; i++) {writeData = writeData + "a";}14、Method may fail to close database resource没有释放数据库资源public ResultSet callProcedure(String procedure) {Session ses = getSessionForUpdate();ResultSet rs = null;try {Connection conn = ses.connection();conn.setAutoCommit(false);CallableStatement statement = conn.prepareCall(procedure); //may fail to close CallableStatementrs = statement.executeQuery();mit();} catch (Exception e) {e.printStackTrace();} finally {try {ses.close();} catch (SQLException e) {throw e;}}return rs;}应当修改为：public ResultSet callProcedure(String procedure) {Session ses = getSessionForUpdate();ResultSet rs = null;CallableStatement statement = null;try {Connection conn = ses.connection();conn.setAutoCommit(false);statement = conn.prepareCall(procedure);rs = statement.executeQuery();mit();} catch (Exception e) {e.printStackTrace();} finally {try {statement.close();ses.close();} catch (SQLException e) {e.printStackTrace();}}return rs;}15、Method may fail to close stream没有关闭流，可能会导致文件描述符泄露，应该在finally中关闭例：try {FileInputStream in = new FileInputStream(file);InputStreamReader inputStreamReader = new InputStreamReader(in);BufferedReader reader = new BufferedReader(inputStreamReader);//...in.close();inputStreamReader.close();reader.close();} catch (IOException e) {修改为：FileInputStream in = null;InputStreamReader inputStreamReader = null;BufferedReader reader = null;try {in = new FileInputStream(file);inputStreamReader = new InputStreamReader(in);reader = new BufferedReader(inputStreamReader);// ...} catch (IOException e) {} finally {try {in.close();} catch (IOException e) {e.printStackTrace();}try {inputStreamReader.close();} catch (IOException e) {e.printStackTrace();}try {reader.close();} catch (IOException e) {e.printStackTrace();}}16、Method might ignore exceptionThis method might ignore an exception. In general, exceptions should be handled or reported in some way, or they should be thrown out of the method.应该将异常处理、打印或者抛出反例：//...} catch (Exception e) {}17、Class defines non-transient non-serializable instance field readerTypeInfo一个实现了Serializable接口的类，含有非transient 和非serializable 的实例对象域。