Question

我不知道如何成功尝试捕获异常。正如您所看到的，我已经启动了try-catch语句，但不知道如何完成它。我收到错误“tractorException.java:83：错误：未报告的异常tractorException;必须被捕获或声明被抛出 setVehicleID（0）; “

import java.io.*;
import java.util.*;
import javax.swing.*;

public class tractorException extends Exception {
    protected int VehicleID; 

    public int setVehicleID(int VehicleID) throws tractorException {
        if (VehicleID <= 0 || VehicleID > 100000) {
            throw new tractorException();
        } else {
            this.VehicleID = VehicleID;
             return this.VehicleID;
        }
    }

    public int getVehicleID() {
        return this.VehicleID;
    }

    tractorException() {
        setVehicleID(0);
    }

    public static void main (String[] args) {
        try {
            throw new Exception("Something went wrong!!");
        } catch (Exception e) {             
        }

Answer 1

将main方法更改为：

public static void main (String[] args) {
      try {
         throw new tractorException(); // infinite loop ensues
      } catch (Exception e) {
         // this catch doesn't matter
      }
}

发生无限循环是因为tractorException的构造函数调用setVehicleID(0)，后者又调用throw new tractorException()，正如您所猜测的那样，调用setVehicleID(0) ...到无限远以及。

Answer 2

必须捕获或声明抛出异常的函数。您的代码所遇到的问题位于setVehicleID(0);行中，如您发布的错误日志中所述。

由于setVehicleID()方法抛出异常，因此无论何时调用此函数，都必须捕获或重新抛出异常。要修复错误，您需要使用try catch：

包围此调用

  tractorException()
  {
     try{
       setVehicleID(0);
     }
     catch( tractorException e ) {
       // Do something with error
     }
  }

Answer 3

尝试输入此

你不能调用Directly setVehicleID方法，因为它有风险的方法

DT1 <- cbind(data.table(loc=c("L1","L2","L3"), product=c("P1","P2","P1")), matrix(10,nrow=3,ncol=12))
setkey(DT1, loc, product)
DT1
   loc product V1 V2 V3 V4 V5 V6 V7 V8 V9 V10 V11 V12
1:  L1      P1 10 10 10 10 10 10 10 10 10  10  10  10
2:  L2      P2 10 10 10 10 10 10 10 10 10  10  10  10
3:  L3      P1 10 10 10 10 10 10 10 10 10  10  10  10
DT2 <- cbind(data.table(loc=c("L2","L3"), product=c("P2","P1")), matrix(1:24,nrow=2,ncol=12))
setkey(DT2, loc, product)
   loc product V1 V2 V3 V4 V5 V6 V7 V8 V9 V10 V11 V12
1:  L2      P2  1  3  5  7  9 11 13 15 17  19  21  23
2:  L3      P1  2  4  6  8 10 12 14 16 18  20  22  24

我在使用try-catch方法处理java中的异常时遇到问题

3 个答案: