【大数据】学习笔记 1 Java SE 第8章 异常 8.3 自定义异常

【大数据】学习笔记

1 Java SE

第8章 异常

8.3 自定义异常

为什么需要自定义异常类:

我们说了Java中不同的异常类,分别表示着某一种具体的异常情况,那么在开发中总是有些异常情况是核心类库中没有定义好的，此时我们需要根据自己业务的异常情况来定义异常类。例如年龄负数问题，考试成绩负数问题等等。

异常类如何定义:

1. 自定义一个编译时异常类型：自定义类 并继承java.lang.Exception。
2. 自定义一个运行时异常类型：自定义类 并继承java.lang.RuntimeException。

注意自定义的异常只能通过throw抛出。

演示自定义异常：

package com.dingjiaxiong.define;

/**
 * @Projectname: BigDataStudy
 * @Classname: NotTriangleException
 * @Author: Ding Jiaxiong
 * @Date:2023/4/27 15:17
 */

public class NotTriangleException extends Exception {
    
    
    public NotTriangleException() {
    
    
    }

    public NotTriangleException(String message) {
    
    
        super(message);
    }
}

package com.dingjiaxiong.define;

/**
 * @Projectname: BigDataStudy
 * @Classname: Triangle
 * @Author: Ding Jiaxiong
 * @Date:2023/4/27 15:17
 */

public class Triangle {
    
    
    private double a;
    private double b;
    private double c;

    public Triangle(double a, double b, double c) throws NotTriangleException {
    
    
        if (a <= 0 || b <= 0 || c <= 0) {
    
    
            throw new NotTriangleException("三角形的边长必须是正数");
        }
        if (a + b <= c || b + c <= a || a + c <= b) {
    
    
            throw new NotTriangleException(a + "," + b + "," + c + "不能构造三角形，三角形任意两边之后必须大于第三边");
        }
        this.a = a;
        this.b = b;
        this.c = c;
    }

    public double getA() {
    
    
        return a;
    }

    public void setA(double a) throws NotTriangleException {
    
    
        if (a <= 0) {
    
    
            throw new NotTriangleException("三角形的边长必须是正数");
        }
        if (a + b <= c || b + c <= a || a + c <= b) {
    
    
            throw new NotTriangleException(a + "," + b + "," + c + "不能构造三角形，三角形任意两边之后必须大于第三边");
        }
        this.a = a;
    }

    public double getB() {
    
    
        return b;
    }

    public void setB(double b) throws NotTriangleException {
    
    
        if (b <= 0) {
    
    
            throw new NotTriangleException("三角形的边长必须是正数");
        }
        if (a + b <= c || b + c <= a || a + c <= b) {
    
    
            throw new NotTriangleException(a + "," + b + "," + c + "不能构造三角形，三角形任意两边之后必须大于第三边");
        }
        this.b = b;
    }

    public double getC() {
    
    
        return c;
    }

    public void setC(double c) throws NotTriangleException {
    
    
        if (c <= 0) {
    
    
            throw new NotTriangleException("三角形的边长必须是正数");
        }
        if (a + b <= c || b + c <= a || a + c <= b) {
    
    
            throw new NotTriangleException(a + "," + b + "," + c + "不能构造三角形，三角形任意两边之后必须大于第三边");
        }
        this.c = c;
    }

    @Override
    public String toString() {
    
    
        return "Triangle{" +
                "a=" + a +
                ", b=" + b +
                ", c=" + c +
                '}';
    }
}

测试类

package com.dingjiaxiong.define;

/**
 * @Projectname: BigDataStudy
 * @Classname: TestTriangle
 * @Author: Ding Jiaxiong
 * @Date:2023/4/27 15:17
 */

public class TestTriangle {
    
    
    public static void main(String[] args) {
    
    
        Triangle t = null;
        try {
    
    
            t = new Triangle(2, 2, 3);
            System.out.println("三角形创建成功：");
            System.out.println(t);
        } catch (NotTriangleException e) {
    
    
            System.err.println("三角形创建失败");
            e.printStackTrace();
        }

        try {
    
    
            if (t != null) {
    
    
                t.setA(1);
            }
            System.out.println("三角形边长修改成功");
        } catch (NotTriangleException e) {
    
    
            System.out.println("三角形边长修改失败");
            e.printStackTrace();
        }
    }
}

测试结果