第九章章节练习

第一题

package com.kgc.zzlx.zhangjie9.zhangjie901;

/**
 * 测试类
 */
public class Test {
    public static void main(String[] args){
        NullError a=new NullError();
        try {
            a.setSex(null);
        }catch (NullPointerException e){
            e.printStackTrace();
        }finally {
            System.err.println("空指针异常......");
        }

    }
}

package com.kgc.zzlx.zhangjie9.zhangjie901;

/**
 * 空指针异常
 */
public class NullError {
    private String sex;

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        if (sex.equals("男")){
            this.sex = sex;
        }else{

        }

    }

    public NullError() {
    }

    public NullError(String sex) {
        this.sex = sex;
    }
}

 

运行结果

 

 

第二题

package com.kgc.zzlx.zhangjie9.zhangjie902;

import java.util.Scanner;

/**
 * 测试类
 */
public class Test {
    public static void main(String[] args){
        Scanner sc=new Scanner(System.in);
        Chengji cj=new Chengji();
        System.out.print("请输入成绩:");
        try{
            cj.setChengji(sc.nextInt());
        }catch (ChengjiError e){
            e.printStackTrace();
        }

    }
}

package com.kgc.zzlx.zhangjie9.zhangjie902;

/**
 * 自定义异常
 */
public class ChengjiError extends Exception {
    public ChengjiError(String a){
        super(a);
    }
}

package com.kgc.zzlx.zhangjie9.zhangjie902;

/**
 * 成绩
 */
public class Chengji {
    private int chengji;

    public int getChengji() {
        return chengji;
    }

    public void setChengji(int chengji) throws ChengjiError{
        if (chengji>=0&&chengji<=100){
            this.chengji = chengji;
        }else{
            throw new ChengjiError("请输入正确的成绩信息!");
        }

    }

    public Chengji() {
    }

    public Chengji(int chengji) {
        this.chengji = chengji;
    }
}

 

运行结果