【JavaSE】异常（异常体系、异常处理方式、自定义异常）
异常介绍
异常体系
一定要能阐述异常的体系结构！
异常类的祖先类：Throwable
所有的异常都是一个类，如果不清楚可以在API帮助文档查询
运行时异常：编译时没有错误，运行时可能会出错，通常是代码不严谨导致的
编译时异常（不包含语法错误）：主要起提醒作用，需要在运行之前给出解决方式
常见的运行时异常：
异常处理方式
异常的默认处理流程
异常处理方式的选择
方式1：try catch捕获异常
方式2：throws抛出异常
throw和throws的区别
Student.java
package com.EveX.domain;
public class Student {
String name;
int age;
public Student() {
}
public Student(String name, int age) {
this.name = name;
this.age = age;
}
/**
* 获取
* @return name
*/
public String getName() {
return name;
}
/**
* 设置
* @param name
*/
public void setName(String name) {
this.name = name;
}
/**
* 获取
* @return age
*/
public int getAge() {
return age;
}
/**
* 设置
* @param age
*/
public void setAge(int age) throws Exception {
if(age > 120 || age < 0) {
throw new Exception("输入年龄范围有误，请重新输入");
}
this.age = age;
}
public String toString() {
return "Student{name = " + name + ", age = " + age + "}";
}
}
ExceptionDemo.java
package com.EveX.exception.handle;
import com.EveX.domain.Student;
import java.util.Scanner;
public class ExceptionDemo {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
Student stu = new Student();
System.out.println("请输入姓名：");
String name = in.nextLine();
stu.setName(name);
System.out.println("请输入年龄：");
int age = 0;
while (true) {
try {
age = Integer.parseInt(in.nextLine());
stu.setAge(age);
break;
} catch (NumberFormatException e) {
System.out.println("NumberFormatException，请重新输入整数：");
} catch (Exception e) {
System.out.println(e.getMessage());
}
}
System.out.println(stu);
}
}
自定义异常
StudentAgeException.java
package com.EveX.exception;
public class StudentAgeException extends RuntimeException{
public StudentAgeException() {
}
public StudentAgeException(String message) {
super(message);
}
}
Student.java
package com.EveX.domain;
import com.EveX.exception.StudentAgeException;
public class Student {
String name;
int age;
public Student() {
}
public Student(String name, int age) {
this.name = name;
setAge(age);
}
/**
* 获取
* @return name
*/
public String getName() {
return name;
}
/**
* 设置
* @param name
*/
public void setName(String name) {
this.name = name;
}
/**
* 获取
* @return age
*/
public int getAge() {
return age;
}
/**
* 设置
* @param age
*/
public void setAge(int age) throws StudentAgeException {
if(age > 120 || age < 0) {
throw new StudentAgeException("输入年龄范围有误，请重新输入");
}
this.age = age;
}
public String toString() {
return "Student{name = " + name + ", age = " + age + "}";
}
}
TryCatchDemo.java
package com.EveX.exception.handle;
import com.EveX.domain.Student;
import com.EveX.exception.StudentAgeException;
import java.util.Scanner;
public class TryCatchDemo {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
Student stu = new Student();
System.out.println("请输入姓名：");
String name = in.nextLine();
stu.setName(name);
System.out.println("请输入年龄：");
int age = 0;
while (true) {
try {
age = Integer.parseInt(in.nextLine());
stu.setAge(age);
break;
} catch (NumberFormatException e) {
System.out.println("NumberFormatException，请重新输入整数：");
} catch (StudentAgeException e) {
System.out.println(e.getMessage());
}
}
System.out.println(stu);
}
}
异常的细节
异常案例练习
需求
代码
ExceptionTest.java
package com.EveX.exception.handle;
import com.EveX.domain.Student;
import com.EveX.exception.StudentAgeException;
import com.EveX.exception.StudentScoreException;
import java.util.Scanner;
public class ExceptionTest {
public static final int MATH = 1;
public static final int CHINESE = 2;
public static final int ENGLISH = 3;
public static Scanner in = new Scanner(System.in);
public static void main(String[] args) {
Student[] stu = new Student[3];
for(int i = 0; i < 3; ++ i ) {
stu[i] = new Student();
System.out.println("请输入第" + (i + 1) + "个学生的信息！");
System.out.print("姓名：");
String name = in.nextLine();
stu[i].setName(name);
int age = 0;
while (true) {
try {
System.out.print("年龄：");
age = Integer.parseInt(in.nextLine());
stu[i].setAge(age);
break;
} catch (NumberFormatException e) {
System.out.println("请确保输入的年龄是整数！");
} catch (StudentAgeException e) {
System.out.println(e.getMessage());
}
}
setScore(stu[i], MATH);
setScore(stu[i], CHINESE);
setScore(stu[i], ENGLISH);
}
for(int i = 0; i < 3; ++ i ) {
System.out.println(stu[i]);
}
}
private static void setScore(Student stu, int subject) {
String msg = "";
switch (subject) {
case MATH -> msg = "数学成绩：";
case CHINESE -> msg = "语文成绩：";
case ENGLISH -> msg = "英语成绩：";
}
double score = 0;
while (true) {
try {
System.out.print(msg);
score = Double.parseDouble(in.nextLine());
switch (subject) {
case MATH -> stu.setMathScore(score);
case CHINESE -> stu.setChineseScore(score);
case ENGLISH -> stu.setEnglishScore(score);
}
break;
} catch (NumberFormatException e) {
System.out.println("请确保输入的成绩是小数！");
} catch (StudentScoreException e) {
System.out.println(e.getMessage());
}
}
}
}
Student.java
package com.EveX.domain;
import com.EveX.exception.StudentAgeException;
import com.EveX.exception.StudentScoreException;
public class Student {
String name;
int age;
double mathScore;
double chineseScore;
double englishScore;
public Student() {
}
public Student(String name, int age, double mathScore, double chineseScore, double englishScore) {
this.name = name;
setAge(age);
setMathScore(mathScore);
setChineseScore(chineseScore);
setEnglishScore(englishScore);
}
/**
* 获取
* @return name
*/
public String getName() {
return name;
}
/**
* 设置
* @param name
*/
public void setName(String name) {
this.name = name;
}
/**
* 获取
* @return age
*/
public int getAge() {
return age;
}
/**
* 设置
* @param age
*/
public void setAge(int age) {
if(age >= 0 && age <= 120) {
this.age = age;
} else {
throw new StudentAgeException("年龄输入有误，请确保年龄在0～120之间！");
}
}
/**
* 获取
* @return mathScore
*/
public double getMathScore() {
return mathScore;
}
/**
* 设置
* @param mathScore
*/
public void setMathScore(double mathScore) {
judge(mathScore);
this.mathScore = mathScore;
}
private static void judge(double score) {
if(score < 0 || score > 100) {
throw new StudentScoreException("请确保输入的成绩在0~100分之间！");
}
}
/**
* 获取
* @return chineseScore
*/
public double getChineseScore() {
return chineseScore;
}
/**
* 设置
* @param chineseScore
*/
public void setChineseScore(double chineseScore) {
judge(chineseScore);
this.chineseScore = chineseScore;
}
/**
* 获取
* @return englishScore
*/
public double getEnglishScore() {
return englishScore;
}
/**
* 设置
* @param englishScore
*/
public void setEnglishScore(double englishScore) {
judge(englishScore);
this.englishScore = englishScore;
}
public String toString() {
return "Student{name = " + name + ", age = " + age + ", mathScore = " + mathScore + ", chineseScore = " + chineseScore + ", englishScore = " + englishScore + "}";
}
}
StudentAgeException.java
package com.EveX.exception;
public class StudentAgeException extends RuntimeException{
public StudentAgeException() {
}
public StudentAgeException(String message) {
super(message);
}
}
StudentScoreException.java
package com.EveX.exception;
public class StudentScoreException extends RuntimeException{
public StudentScoreException() {
}
public StudentScoreException(String message) {
super(message);
}
}
