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skill_tree_java
提交 432c302c 编写于 作者: ccat's avatar ccat
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Merge branch 'dev/exception' into 'master' 

dev(hansbug): add problems in exception part

See merge request !2
上级 e19310cf 173c3115
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data/1.Java初阶/9.控制执行流程/4.通过异常处理错误/checked_exception.json 0 → 100644
浏览文件 @ 432c302c
{
"type": "code_options",
"author": "HansBug",
"source": "checked_exception.md",
"notebook_enable": false,
"exercise_id": "302ed00decc24b4ba435aab028582ac4"
}
\ No newline at end of file
data/1.Java初阶/9.控制执行流程/4.通过异常处理错误/checked_exception.md 0 → 100644
浏览文件 @ 432c302c
# 自定义可查异常（Checked Exception）
现有如下的学生考试成绩查询程序，会根据给定的字符串格式`studentID`进行学生分数查询，如果该学生存在，则返回其分数（确保为非负整数）；如果该学生不存在，则返回`-1`，如下所示
```java
public class TestMain {
private static boolean containsStudent(String studentID) {
// Return true when the given `studentID` represents an existing student.
}
private static int queryScore(String studentID) {
// Get and then return score of the student
// whose ID is `StudentID` from the database.
}
private static int getScoreByStudentID(String studentID) {
if (containsStudent(studentID)) {
return queryScore(studentID);
} else {
return -1;
}
}
public static void main(String[] args) {
String studentID = "ID20211224";
int score = getScoreByStudentID(studentID);
if (score >= 0) {
System.out.printf("Student ID : %s%n", studentID);
System.out.printf("Score : %d%n", score);
} else {
System.out.printf("Student ID %s not found!%n", studentID);
}
}
}
```
请改写上述代码，对于学生不存在的情况，**使用可查异常（Checked Exception）对潜在的异常情况进行妥善处理**而不是返回`-1`。
> 可查异常（Checked Exception）是编译器在编译时会进行检查，也称为编译时异常（Compile Time Exception）。 这些异常往往具备可预见性，且不能简单地被忽略，编程者应当对其进行妥善处理。
因此，下列修改方式正确的是：
## 答案
```java
public class TestMain {
private static boolean containsStudent(String studentID) {
// Return true when the given `studentID` represents an existing student.
}
private static int queryScore(String studentID) {
// Get and then return score of the student
// whose ID is `StudentID` from the database.
}
public static class StudentNotExistException extends Exception {
public StudentNotExistException(String studentID) {
super(String.format("Student ID %s not found.", studentID));
}
}
private static int getScoreByStudentID(String studentID) throws StudentNotExistException {
if (containsStudent(studentID)) {
return queryScore(studentID);
} else {
throw new StudentNotExistException(studentID);
}
}
public static void main(String[] args) {
String studentID = "ID20211224";
try {
int score = getScoreByStudentID(studentID);
System.out.printf("Student ID : %s%n", studentID);
System.out.printf("Score : %d%n", score);
} catch (StudentNotExistException err) {
System.out.printf("Student ID %s not found!%n", studentID);
}
}
}
```
## 选项
### A
```java
public class TestMain {
private static boolean containsStudent(String studentID) {
// Return true when the given `studentID` represents an existing student.
}
private static int queryScore(String studentID) {
// Get and then return score of the student
// whose ID is `StudentID` from the database.
}
public static class StudentNotExistException extends RuntimeException {
public StudentNotExistException(String studentID) {
super(String.format("Student ID %s not found.", studentID));
}
}
private static int getScoreByStudentID(String studentID) throws StudentNotExistException {
if (containsStudent(studentID)) {
return queryScore(studentID);
} else {
throw new StudentNotExistException(studentID);
}
}
public static void main(String[] args) {
String studentID = "ID20211224";
try {
int score = getScoreByStudentID(studentID);
System.out.printf("Student ID : %s%n", studentID);
System.out.printf("Score : %d%n", score);
} catch (StudentNotExistException err) {
System.out.printf("Student ID %s not found!%n", studentID);
}
}
}
```
### B
```java
public class TestMain {
private static boolean containsStudent(String studentID) {
// Return true when the given `studentID` represents an existing student.
}
private static int queryScore(String studentID) {
// Get and then return score of the student
// whose ID is `StudentID` from the database.
}
public static class StudentNotExistException extends RuntimeException {
public StudentNotExistException(String studentID) {
super(String.format("Student ID %s not found.", studentID));
}
}
private static int getScoreByStudentID(String studentID) {
if (containsStudent(studentID)) {
return queryScore(studentID);
} else {
throw new StudentNotExistException(studentID);
}
}
public static void main(String[] args) {
String studentID = "ID20211224";
int score = getScoreByStudentID(studentID);
System.out.printf("Student ID : %s%n", studentID);
System.out.printf("Score : %d%n", score);
}
}
```
### C
```java
public class TestMain {
private static boolean containsStudent(String studentID) {
// Return true when the given `studentID` represents an existing student.
}
private static int queryScore(String studentID) {
// Get and then return score of the student
// whose ID is `StudentID` from the database.
}
public static class StudentNotExistException extends Error {
public StudentNotExistException(String studentID) {
super(String.format("Student ID %s not found.", studentID));
}
}
private static int getScoreByStudentID(String studentID) throws StudentNotExistException {
if (containsStudent(studentID)) {
return queryScore(studentID);
} else {
throw new StudentNotExistException(studentID);
}
}
public static void main(String[] args) {
String studentID = "ID20211224";
try {
int score = getScoreByStudentID(studentID);
System.out.printf("Student ID : %s%n", studentID);
System.out.printf("Score : %d%n", score);
} catch (StudentNotExistException err) {
System.out.printf("Student ID %s not found!%n", studentID);
}
}
}
```
### D
```java
public class TestMain {
private static boolean containsStudent(String studentID) {
// Return true when the given `studentID` represents an existing student.
}
private static int queryScore(String studentID) {
// Get and then return score of the student
// whose ID is `StudentID` from the database.
}
public static class StudentNotExistException extends Exception {
public StudentNotExistException(String studentID) {
super(String.format("Student ID %s not found.", studentID));
}
}
private static int getScoreByStudentID(String studentID) throws StudentNotExistException {
if (containsStudent(studentID)) {
return queryScore(studentID);
} else {
throw new StudentNotExistException(studentID);
}
}
public static void main(String[] args) {
String studentID = "ID20211224";
try {
int score = getScoreByStudentID(studentID);
System.out.printf("Student ID : %s%n", studentID);
System.out.printf("Score : %d%n", score);
} except (StudentNotExistException err) {
System.out.printf("Student ID %s not found!%n", studentID);
}
}
}
```
data/1.Java初阶/9.控制执行流程/4.通过异常处理错误/config.json
浏览文件 @ 432c302c
...@@ -223,7 +223,9 @@ ...@@ -223,7 +223,9 @@
], ],
"export": [ "export": [
"exception.json", "exception.json",
"using.json" "using.json",
"runtime_exception.json",
"checked_exception.json"
], ],
"title": "通过异常处理错误" "title": "通过异常处理错误"
} }
\ No newline at end of file
data/1.Java初阶/9.控制执行流程/4.通过异常处理错误/runtime_exception.json 0 → 100644
浏览文件 @ 432c302c
{
"type": "code_options",
"author": "HansBug",
"source": "runtime_exception.md",
"notebook_enable": false,
"exercise_id": "61a61ce93dca4b2e9049f5318e4d2a21"
}
\ No newline at end of file
data/1.Java初阶/9.控制执行流程/4.通过异常处理错误/runtime_exception.md 0 → 100644
浏览文件 @ 432c302c
# 自定义运行时异常（RuntimeException）
现有如下的海伦公式计算函数，根据三角形的三条边长`a`、`b`和`c`（均确保大于0）计算三角形的面积。当三角形本身非法时返回负数，否则返回面积，如下所示
```java
public class TestMain {
private static float getArea(float a, float b, float c) {
if ((a + b < c) || (a + c < b) || (b + c < a)) {
return -1; // 非法三角形
} else {
float p = (a + b + c) / 2;
return (float) Math.sqrt((p - a) * (p - b) * (p - c) * p); // 海伦公式
}
}
public static void main(String[] args) {
System.out.println(TestMain.getArea(3, 4, 5));
}
}
```
请改写上述代码，对于三角形非法的情况，**仅在运行抛出不可查异常（Unchecked Exception）**而不是返回`-1`。
> 不可查异常（Unchecked Exception）指在运行时发生的异常。这些也被称为运行时异常（Runtime Exception）。其中包括程序逻辑错误或API使用不当等，例如ArrayIndexOutOfBoundsException、IllegalStateException与NullPointerException等，此类异常将在编译时忽略，仅在运行时处理。
因此，下列修改方式正确的是：
## 答案
```java
public class TestMain {
public static class InvalidTriangleException extends RuntimeException {
public InvalidTriangleException(float a, float b, float c) {
super(String.format("Invalid triangle - (%.3f, %.3f, %.3f).", a, b, c));
}
}
private static float getArea(float a, float b, float c) {
if ((a + b < c) || (a + c < b) || (b + c < a)) {
throw new InvalidTriangleException(a, b, c);
} else {
float p = (a + b + c) / 2;
return (float) Math.sqrt((p - a) * (p - b) * (p - c) * p);
}
}
public static void main(String[] args) {
System.out.println(TestMain.getArea(3, 4, 5));
}
}
```
## 选项
### A
```java
public class TestMain {
public class InvalidTriangleException extends RuntimeException {
public InvalidTriangleException(float a, float b, float c) {
super(String.format("Invalid triangle - (%.3f, %.3f, %.3f).", a, b, c));
}
}
private float getArea(float a, float b, float c) {
if ((a + b < c) || (a + c < b) || (b + c < a)) {
throw new InvalidTriangleException(a, b, c);
} else {
float p = (a + b + c) / 2;
return (float) Math.sqrt((p - a) * (p - b) * (p - c) * p);
}
}
public static void main(String[] args) {
System.out.println(TestMain.getArea(3, 4, 5));
}
}
```
### B
```java
public class TestMain {
public static class InvalidTriangleException extends Exception {
public InvalidTriangleException(float a, float b, float c) {
super(String.format("Invalid triangle - (%.3f, %.3f, %.3f).", a, b, c));
}
}
private static float getArea(float a, float b, float c) {
if ((a + b < c) || (a + c < b) || (b + c < a)) {
throw new InvalidTriangleException(a, b, c);
} else {
float p = (a + b + c) / 2;
return (float) Math.sqrt((p - a) * (p - b) * (p - c) * p);
}
}
public static void main(String[] args) {
System.out.println(TestMain.getArea(3, 4, 5));
}
}
```
### C
```java
public class TestMain {
public static class InvalidTriangleException extends Exception {
public InvalidTriangleException(float a, float b, float c) {
super(String.format("Invalid triangle - (%.3f, %.3f, %.3f).", a, b, c));
}
}
private static float getArea(float a, float b, float c) throws InvalidTriangleException {
if ((a + b < c) || (a + c < b) || (b + c < a)) {
throw new InvalidTriangleException(a, b, c);
} else {
float p = (a + b + c) / 2;
return (float) Math.sqrt((p - a) * (p - b) * (p - c) * p);
}
}
public static void main(String[] args) throws InvalidTriangleException {
System.out.println(TestMain.getArea(3, 4, 5));
}
}
```
### D
```java
public class TestMain {
public static class InvalidTriangleException extends Error {
public InvalidTriangleException(float a, float b, float c) {
super(String.format("Invalid triangle - (%.3f, %.3f, %.3f).", a, b, c));
}
}
private static float getArea(float a, float b, float c) {
if ((a + b < c) || (a + c < b) || (b + c < a)) {
throw new InvalidTriangleException(a, b, c);
} else {
float p = (a + b + c) / 2;
return (float) Math.sqrt((p - a) * (p - b) * (p - c) * p);
}
}
public static void main(String[] args) {
System.out.println(TestMain.getArea(3, 4, 5));
}
}
```
### E
```java
public class TestMain {
public static class InvalidTriangleException extends RuntimeException {
public InvalidTriangleException(float a, float b, float c) {
super(String.format("Invalid triangle - (%.3f, %.3f, %.3f).", a, b, c));
}
}
private static float getArea(float a, float b, float c) throws InvalidTriangleException {
if ((a + b < c) || (a + c < b) || (b + c < a)) {
throw new InvalidTriangleException(a, b, c);
} else {
float p = (a + b + c) / 2;
return (float) Math.sqrt((p - a) * (p - b) * (p - c) * p);
}
}
public static void main(String[] args) throws InvalidTriangleException {
System.out.println(TestMain.getArea(3, 4, 5));
}
}
```
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