private static void readFile(String filePath) throws IOException {
File file = new File(filePath);
String result;
BufferedReader reader = new BufferedReader(new FileReader(file));
while((result = reader.readLine())!=null) {
System.out.println(result);
}
reader.close();
}
private static void readFile(String filePath) throws MyException {
try {
// code
} catch (IOException e) {
MyException ex = new MyException("read file failed.");
ex.initCause(e);
throw ex;
}
}
private static void readFile(String filePath) {
try {
// code
} catch (FileNotFoundException e) {
// handle FileNotFoundException
} catch (IOException e){
// handle IOException
}
}
private static void readFile(String filePath) {
try {
// code
} catch (FileNotFoundException | UnknownHostException e) {
// handle FileNotFoundException or UnknownHostException
} catch (IOException e){
// handle IOException
}
}
public class MyException extends Exception {
public MyException(){ }
public MyException(String msg){
super(msg);
}
// ...
}
private static void readFile(String filePath) throws MyException {
File file = new File(filePath);
String result;
BufferedReader reader = null;
try {
reader = new BufferedReader(new FileReader(file));
while((result = reader.readLine())!=null) {
System.out.println(result);
}
} catch (IOException e) {
System.out.println("readFile method catch block.");
MyException ex = new MyException("read file failed.");
ex.initCause(e);
throw ex;
} finally {
System.out.println("readFile method finally block.");
if (null != reader) {
try {
reader.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
catch (IOException e) {
System.out.println("readFile method catch block.");
return;
}
readFile method catch block. readFile method finally block.
private static void tryWithResourceTest(){
try (Scanner scanner = new Scanner(new FileInputStream("c:/abc"),"UTF-8")){
// code
} catch (IOException e){
// handle exception
}
}
public static int getInt() {
int a = 10;
try {
System.out.println(a / 0);
a = 20;
} catch (ArithmeticException e) {
a = 30;
return a;
/*
* return a 在程序执行到这一步的时候，这里不是return a 而是 return 30；这个返回路径就形成了
* 但是呢，它发现后面还有finally，所以继续执行finally的内容，a=40
* 再次回到以前的路径,继续走return 30，形成返回路径之后，这里的a就不是a变量了，而是常量30
*/
} finally {
a = 40;
}
return a;
}
public static int getInt() {
int a = 10;
try {
System.out.println(a / 0);
a = 20;
} catch (ArithmeticException e) {
a = 30;
return a;
} finally {
a = 40;
//如果这样，就又重新形成了一条返回路径，由于只能通过1个return返回，所以这里直接返回40
return a;
}
}
try {
throw new ExampleB("b")
} catch（ExampleA e）{
System.out.println("ExampleA");
} catch（Exception e）{
System.out.println("Exception");
}
class Annoyance extends Exception {
}
class Sneeze extends Annoyance {
}
class Human {
public static void main(String[] args)
throws Exception {
try {
try {
throw new Sneeze();
} catch ( Annoyance a ) {
System.out.println("Caught Annoyance");
throw a;
}
} catch ( Sneeze s ) {
System.out.println("Caught Sneeze");
return ;
} finally {
System.out.println("Hello World!");
}
}
}
Caught Annoyance Caught Sneeze Hello World!
public void doNotCloseResourceInTry() {
FileInputStream inputStream = null;
try {
File file = new File("./tmp.txt");
inputStream = new FileInputStream(file);
// use the inputStream to read a file
// do NOT do this
inputStream.close();
} catch (FileNotFoundException e) {
log.error(e);
} catch (IOException e) {
log.error(e);
}
}
public void closeResourceInFinally() {
FileInputStream inputStream = null;
try {
File file = new File("./tmp.txt");
inputStream = new FileInputStream(file);
// use the inputStream to read a file
} catch (FileNotFoundException e) {
log.error(e);
} finally {
if (inputStream != null) {
try {
inputStream.close();
} catch (IOException e) {
log.error(e);
}
}
}
}
public void automaticallyCloseResource() {
File file = new File("./tmp.txt");
try (FileInputStream inputStream = new FileInputStream(file);) {
// use the inputStream to read a file
} catch (FileNotFoundException e) {
log.error(e);
} catch (IOException e) {
log.error(e);
}
}
public void doNotDoThis() throws Exception {
...
}
public void doThis() throws NumberFormatException {
...
}
public void doSomething(String input) throws MyBusinessException {
...
}
try {
new Long("xyz");
} catch (NumberFormatException e) {
log.error(e);
}
public void catchMostSpecificExceptionFirst() {
try {
doSomething("A message");
} catch (NumberFormatException e) {
log.error(e);
} catch (IllegalArgumentException e) {
log.error(e)
}
}
public void doNotCatchThrowable() {
try {
// do something
} catch (Throwable t) {
// don't do this!
}
}
public void doNotIgnoreExceptions() {
try {
// do something
} catch (NumberFormatException e) {
// this will never happen
}
}
public void logAnException() {
try {
// do something
} catch (NumberFormatException e) {
log.error("This should never happen: " e);
}
}
try {
new Long("xyz");
} catch (NumberFormatException e) {
log.error(e);
throw e;
}
17:44:28,945 ERROR TestExceptionHandling:65 - java.lang.NumberFormatException: For input string: "xyz" Exception in thread "main" java.lang.NumberFormatException: For input string: "xyz" at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65) at java.lang.Long.parseLong(Long.java:589) at java.lang.Long.(Long.java:965) at com.stackify.example.TestExceptionHandling.logAndThrowException(TestExceptionHandling.java:63) at com.stackify.example.TestExceptionHandling.main(TestExceptionHandling.java:58)
public void wrapException(String input) throws MyBusinessException {
try {
// do something
} catch (NumberFormatException e) {
throw new MyBusinessException("A message that describes the error.", e);
}
}
public void wrapException(String input) throws MyBusinessException {
try {
// do something
} catch (NumberFormatException e) {
throw new MyBusinessException("A message that describes the error.", e);
}
}
private int x = 0;
public int checkReturn() {
try {
// x等于1，此处不返回
return x;
} finally {
// 返回的结果是2
return x;
}
}
END 十期推荐 【231期】面试官：Java中 serialVersionUID 的作用是什么？ 【232期】面试官：Spring的 IOC 容器比New对象究竟好在哪? 【233期】面试官：什么是耦合？解耦合的方法有哪几种？ 【234期】30个 Java 集合面试必备的问题和答案 【235期】面试官：Redis的数据是存在内存里吗？谈谈Redis各种数据类型的使用场景？ 【236期】面试官：线程池中多余的线程是如何回收的？ 【237期】面试官：如何发现 Redis 热点 Key ，解决方案有哪些？ 【238期】面试官：Redis新版本开始引入多线程，谈谈你的看法？ 【239期】面试官：如何使用Redis实现电商系统的库存扣减？ 【240期】面试官：你了解JVM的内存溢出吗？ ？ ~