动手动脑:Finally

Ø当有多个嵌套的try…catch…finally时,要特别注意finally的执行时机。
Ø请先阅读 EmbedFinally.java示例,再运行它,观察其输出并进行总结。
Ø特别注意:
Ø当有多层嵌套的finally时,异常在不同的层次抛出  ,在不同的位置抛出,可能会导致不同的finally语句块执行顺序。

EmbedFinally.java示例

public class EmbededFinally {

public static void main(String args[]) {

int result;

try {

System.out.println("in Level 1");

try {

System.out.println("in Level 2");
// result=100/0; //Level 2

try {

System.out.println("in Level 3");

result=100/0; //Level 3

}

catch (Exception e) {

System.out.println("Level 3:" + e.getClass().toString());

}

finally {

System.out.println("In Level 3 finally");

}

// result=100/0; //Level 2

}

catch (Exception e) {

System.out.println("Level 2:" + e.getClass().toString());

}
finally {

System.out.println("In Level 2 finally");

}

// result = 100 / 0; //level 1

}

catch (Exception e) {

System.out.println("Level 1:" + e.getClass().toString());

}

finally {

System.out.println("In Level 1 finally");

}

}

}

动手动脑:Finally

Ø辨析:finally语句块一定会执行吗?
Ø请通过 SystemExitAndFinally.java示例程序回答上述问题
 
 

public class SystemExitAndFinally {

public static void main(String[] args)
{
try{

System.out.println("in main");
throw new Exception("Exception is thrown in main");
//System.exit(0);

}
catch(Exception e)
{
System.out.println(e.getMessage());
System.exit(0);
}
finally
{
System.out.println("in finally");
}
}

}

动手动脑:Finally

Finally语句没有执行!

public class SystemExitAndFinally {

public static void main(String[] args)
{
try{

System.out.println("in main");
throw new Exception("Exception is thrown in main");
//System.exit(0);

}
catch(Exception e)
{
System.out.println(e.getMessage());
//System.exit(0);
}
finally
{
System.out.println("in finally");
}
}

}

动手动脑:Finally

Finally语句执行了!

所以,Finally语句块不一定会执行!得看返回值的位置在哪里。

上一篇:C# 编程指南-事件


下一篇:微信小程序想要的是无法监测的流量dark social