关键字 | 作用描述 |
---|---|
try{ } | 可能抛出异常的代码放在try语句块内,当try语句块内发生异常时,异常会被抛出 |
catch(e) | 捕获异常e; catch用来捕获try语句块中发生的异常,可以声明多个catch,catch里也可以捕捉多个异常 |
finally | finally语句块总会被执行。主要用于回收在try代码块里打开的资源(如数据库连接、TCP连接和文件流) |
throw | 用于抛出异常 |
throws | 声明该方法可能抛出的异常 |
public int hello(String fileName) throws RuntimeException{
int a = 10;
try{
File file = new File(fileName);
FileInputStream in = new FileInputStream(file);
return a; // 返回值10
}catch (FileNotFoundException e){
System.out.println("error occurred");
}catch (ArithmeticException | IndexOutOfBoundsException e){
System.out.println("whatever");
} finally{
System.out.println("finally");
a = 20; // finally修改a,也不会改变try里 return 10 的结局
// return a; //如果此处返回,则返回值等于 20
}
return -1;
}
File file = new File("./text.txt");
try (FileInputStream in =new FileInputStream(file)){
...//数据操作
} catch (Exception e) {
log.error(e.getMessage(), e);
...
}
//以list的方式得到throwable的异常链
public static List<Throwable> getCausalChain(Throwable throwable)
//返回最底层的异常
public static Throwable getRootCause(Throwable throwable)
//把受检查的异常转换为运行时异常
//获取异常调用链的描述输出(每一行都有)
public static String getStackTraceAsString(Throwable throwable)
//如果异常是declaredType类似,则抛出异常,传递throwable
public static <X extends Throwable> void propagateIfInstanceOf(
@Nullable Throwable throwable, Class<X> declaredType) throws X
//当且仅当它是一个RuntimeException和Error时,或者是一个X的实例时,传递throwable
void propagateIfPossible(Throwable, Class<X extends Throwable>) throws X
//将Throwable转为RuntimeException,不建议使用此方法
public static RuntimeException propagate(Throwable throwable)
public static void main(String args[]) throws FileNotFoundException {
try {
File file = new File("./text.txt");
FileInputStream inputStream = new FileInputStream(file);
} catch (Exception e) {
//获取异常调用栈信息,并打印(或者保存在其他地方)
String errorMsg = Throwables.getStackTraceAsString(e);
System.out.println(errorMsg);
//如果e是FileNotFoundException,直接抛出
Throwables.propagateIfInstanceOf(e, FileNotFoundException.class);
//其他Throwable 转为 RuntimeException类抛出
throw Throwables.propagate(e);
}
}
[1]
Java异常面试题: https://thinkwon.blog.csdn.net/article/details/104390689
[2]
Guava的异常工具类--Throwables: https://www.cnblogs.com/rollenholt/p/3527645.html