Java 面向对象设计 - Java 终止块
try 块也可以有零个或一个 finally 块。 finally 块总是与 try 块一起使用。
语法
使用 finally 块的语法是
finally {// Code for finally block
}
finally 块以关键字 finally 开始，后面紧跟一对大括号。
finally 块的代码放在大括号内。
try，catch 和 finally 块有两种可能的组合: try - catch - finally 或 try - finally 。
try 块可以后跟零个或多个 catch 块。
try 块最多可以有一个 finally 块。
try 块必须有一个 catch 块，一个 finally 块，或者两者兼而有之。
try-catch-finally 块的语法是：
try {// Code for try block
}
catch(Exception1 e1) {// Code for catch block
}
finally {// Code for finally block
}
try - finally 块的语法是：
try {// Code for try block
}
finally {// Code for finally block
}
无论在相关联的 try 和 / 或 catch 块中发生什么，finally 块都被保证被执行。
通常，我们使用 finally 块来写清理代码。
例如，我们可能获得一些资源，当我们完成它们时，必须释放。
try - finally 块允许你实现这个逻辑。
您的代码结构将如下所示:
try {// Obtain and use some resources here
}
finally {// Release the resources that were obtained in the try block
}例子
下面的代码演示了 finally 块的使用。
public class Main {public static void main(String[] args) {int x = 10, y = 0, z = 0;try {System.out.println("Before dividing x by y.");z = x / y;System.out.println("After dividing x by y.");} catch (ArithmeticException e) {System.out.println("Inside catch block a.");} finally {System.out.println("Inside finally block a.");}try {System.out.println("Before setting z to 2.");z = 2;System.out.println("After setting z to 2.");}catch (Exception e) {System.out.println("Inside catch block b.");} finally {System.out.println("Inside finally block b.");}try {System.out.println("Inside try block c.");}finally {System.out.println("Inside finally block c.");}try {System.out.println("Before executing System.exit().");System.exit(0);System.out.println("After executing System.exit().");} finally {// This finally block will not be executed// because application exits in try blockSystem.out.println("Inside finally block d.");}}
}
上面的代码生成以下结果。
重新引用异常
捕获的异常可以重新引用。
public class Main {public static void main(String[] args) {try {m1();} catch (MyException e) {// Print the stack trace e.printStackTrace();}}public static void m1() throws MyException {try {m2();} catch (MyException e) {e.fillInStackTrace();throw e;}}public static void m2() throws MyException {throw new MyException("An error has occurred.");}
}class MyException extends Exception {public MyException() {super();}public MyException(String message) {super(message);}public MyException(String message, Throwable cause) {super(message, cause);}public MyException(Throwable cause) {super(cause);}
}
上面的代码生成以下结果。
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