我正在尝试为我的应用程序创建自定义例外。它生成一个随机数，从BufferedReader获取一个字符，通过枚举将该字符与int相关联，并输出int是否高于，低于或等于random int。然后你可以再玩一次。
我有三个错误。在我的两个自定义异常类中，我得到一个删除标记'{'，{class body {的错误。然后，对于我的BufferedReader，.readline（）方法抛出IOException。所以我的自定义异常NewIOException扩展了IOException并添加了try，catch和finally块来捕获它。我收到错误“Unhandled Exception type IOException”，即使我的自定义异常扩展了IOException。我究竟做错了什么？我环顾四周，我没有看到任何可以照顾的事情。自定义异常扩展IOException和我读过的自定义异常都没有什么是简短的，没有帮助。我有一本书“学习Java for Android Development”，但代码示例并没有真正涵盖它。
这是我的代码。
package randomInt;
import java.util.Random;
import java.util.StringTokenizer;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.lang.Character;
public class Guess{
int getNewRandom(){
Random rand = new Random();
int num = rand.nextInt(25);
return num;
}
public void userInput() throws StringLengthException, NewIOException'{
System.out.println("Guess a letter between a and z: ");
int intRandom = getNewRandom();
try{
BufferedReader cin = new BufferedReader(new InputStreamReader(System.in));`
String string= cin.readLine();
//StringTokenizer tokenizer = new StringTokenizer(string);
int length = string.length();
if(length > 1){
throw new StringLengthException();
}
//String[] stringToToken = new String[numTokens];
char guess = string.charAt(0);
char ch = Character.toLowerCase(guess);
//GuessDeterminer determine = new GuessDeterminer(ch);
int x = GuessDeterminer.determineGuess(ch);
if(x > intRandom){
System.out.println("Your guess is too high.");
System.out.println("Choose again: ");
userInput();
}
else if(x < intRandom){
System.out.println("Your guess is too low.");
System.out.println("Choose again: ");
userInput();
}
else if(x == intRandom){
System.out.println("Your correct, congratulations!");
System.out.println("Play again!");
System.out.println("Guess a letter between a and z: ");
getNewRandom();
userInput();
}
}
catch (NewIOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
finally{
System.out.println("Guess a letter between a and z: ");
getNewRandom();
userInput();
}
}
}
package randomInt;
public class StringLengthException extends Exception{
super("A new letter of length one from a - z must be chosen.");
super("Choose a letter: ");
Guess.userInput();
}
package randomInt;
import java.io.IOException;
public class NewIOException extends IOException{
super("Input Error");
System.out.println("Input new letter from a - z: ");
Guess.userInput();
}
package randomInt;
public enum GuessDeterminer {
a('a'),
b('b'),
c('c'),
d('c'),
e('c'),
f('c'),
g('c'),
h('c'),
i('c'),
j('c'),
k('c'),
l('c'),
m('c'),
n('c'),
o('c'),
p('c'),
q('c'),
r('c'),
s('c'),
t('c'),
u('c'),
v('c'),
w('c'),
x('c'),
y('c'),
z('c');
private final char character;
public final int returnAnswer;
GuessDeterminer(char character){
this.character = character;
this.returnAnswer = determineGuess(character);
}
static int determineGuess(char ch){
int x = 0;
switch(ch){
case 'a' : x = 0;
case 'b' : x = 1;
case 'c' : x = 2;
case 'd' : x = 3;
case 'e' : x = 4;
case 'f' : x = 5;
case 'g' : x = 6;
case 'h' : x = 7;
case 'i' : x = 8;
case 'j' : x = 9;
case 'k' : x = 10;
case 'l' : x = 11;
case 'm' : x = 12;
case 'n' : x = 13;
case 'o' : x = 14;
case 'p' : x = 15;
case 'q' : x = 16;
case 'r' : x = 17;
case 's' : x = 18;
case 't' : x = 19;
case 'u' : x = 20;
case 'v' : x = 21;
case 'w' : x = 22;
case 'x' : x = 23;
case 'y' : x = 24;
case 'z' : x = 25;
}
return x;
}
}
这些是我对异常类的编辑。我对Guess.userInput（）的调用需要在两个异常类中抛出StringLengthException，我不知道这是不是正确的举动。我的异常类中的扩展，Guess.java的throws子句中的逗号，以及紧接在println语句下面的错误也有错误。这些错误的性质在下面的评论中解释。
public class StringLengthException extends Exception throws StringLenthException{
public StringLengthException(){
super("StringLengthException thrown.");
System.out.println("A new letter of length one from a - z must be chosen.");
System.out.println("Choose a letter: ");
Guess.userInput();
}
}
public class NewIOException extends IOException throws StringLengthException{
public NewIOException(){
super("Input Error");
System.out.println("Input new letter from a - z: ");
Guess.userInput();
}
}
答案 0 :(得分：0)
此代码：
super("Input Error");
System.out.println("Input new letter from a - z: ");
Guess.userInput();
应该在构造函数中：
public class NewIOException extends IOException{
public NewIOException () {
super("Input Error");
// though it's a bad practice to
// have this logic in the exception class
System.out.println("Input new letter from a - z: ");
Guess.userInput();
}
}
您的其他异常类中存在相同的错误 - StringLengthException。
但是，即使您修复了编译错误，异常也不应包含处理异常的代码。这就是catch块的用途。
代码中的另一个问题 - 当你有catch (NewIOException e)时，该子句不会捕获IOException的{{1}}。因此，您应该有一个NewIOException子句。实际上，我看不到你抛出catch (IOException e)的位置，所以你应该只抓住NewIOException。
你的捕获块看起来像这样：
IOException另请注意，如果捕获异常 catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
，则方法签名中不需要X子句。您要么捕获异常，要么声明您的方法throws X。
我注意到的另一个错误：
从异常类中删除throws子句。该子句仅用于方法。