JAVA常用类作业（Chapter13）

第十三章作业

第十三章作业
- 1.将字符串指定部分进行反转
- 2.用户注册
- 3.按照格式输出名字信息
- 4.判断字符类型
- 5.String内存分布

第十三章作业 1.将字符串指定部分进行反转

字符翻转，如何实现
逻辑判断，选出正确的条件，然后取反即可。

抛出异常，然后使用 try catch处理

package com.homework13;


public class Homework01 {
    public static void main(String[] args) {
        String str = "abcdefghijklmn";
        try{
            str = reverse(str, 1, 5);
        } catch(Exception e){
            System.out.println(e.getMessage());
            return;
        }
        System.out.println(str);
    }
    public static String reverse(String str,int start,int end){
        if (!(str != null && start >= 0 && end > start && end < str.length())){
            throw new RuntimeException("参数不正确");
        }
        char[] chars = str.toCharArray();
        char temp = ' ';
        for (int i = start, j = end; i < j; i++,j--) {
            temp = chars[j];
            chars[j] = chars[i];
            chars[i] = temp;
        }

        return new String(chars);
    }
}

2.用户注册

使用到的函数 str.indexof(’ ');//得到字符的位置
对用户信息进行逻辑判断，选出正确的条件取反即可。
字符串是否都是数字，将字符串转成数组，再判断每一项是否都在’0‘ - '9’之间即可；

不满足条件，抛出异常即可

package com.homework13;

import java.util.Scanner;


public class Homework02 {
    public static void main(String[] args) {
        Person person = new Person();
        String name = "jack";
        String pwd = "123456";
        String email = "123@ .343";

        try {
            person.userRegister(name,pwd,email);
            System.out.println("注册成功");
        } catch (Exception e) {
            System.out.println(e.getMessage());
            System.out.println("注册失败");
        }
        System.out.println(person.toString());
    }
}
class Person{
    private String name = " ";
    private String pwd = " ";
    private String email = " ";

    public Person() {
    }

    public Person(String name, String pwd, String email) {
        setName(name);
        setPwd(pwd);
        setEmail(email);
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        if (name.length() > 4 || name.length() < 2){
//            System.out.println("姓名长度输入错误（2-4之间）");
            throw new RuntimeException("姓名长度输入错误（2-4之间）");
        }
        this.name = name;
    }

    public String getPwd() {
        return pwd;
    }

    public void setPwd(String pwd) {
        if (pwd.length()!=6){
//            System.out.println("密码长度有误！！");
            throw new RuntimeException("密码长度有误！！");

        }
        char chars[] = pwd.toCharArray();
        for (int i = 0; i < chars.length; i++) {
            if (chars[i] > '9' || chars[i] < '0'){
//                System.out.println("密码只能是数字");
                throw new RuntimeException("密码只能是数字");
            }
        }
        this.pwd = pwd;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        int index1 = email.indexOf('@');
        int index2 = email.indexOf('.');
        if (!(index1 != -1  && index2 !=-1 && index1 == index2 -1)){
            System.out.println("格式错误");
            throw new RuntimeException("邮箱格式错误");
        }
        this.email = email;
    }
    public void userRegister(String name, String pwd, String email){
        setName(name);
        setPwd(pwd);
        setEmail(email);
    }

    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + ''' +
                ", pwd='" + pwd + ''' +
                ", email='" + email + ''' +
                '}';
    }
}

3.按照格式输出名字信息

函数：str.substring(start,end);//得到子字符串
split(" ");//按照空格分隔，老师用的这种，得到字符串数组
String.format()函数，按照一定格式转换得到字符串

package com.homework13;


public class Homework03 {
    public static void main(String[] args) {
        String name = "Hancvv ghunff Pfssing";
        printName(name);
    }
//    public static  void printName(String name){//简陋版本
//        int index1 = name.indexOf(' ');
//        int index2 = name.lastIndexOf(' ');
//        String str1 = name.substring(0,index1);
//        String str2 = name.substring(index1 + 1, index2  - 1);
//        String str3 = name.substring(index2 + 1);
//        System.out.println(str3 + "," + str1 + "." + str2.substring(0,1).toUpperCase());
//    }
    public static  void printName(String name){//简陋版本
        if (name == null){
            System.out.println("name 不能为空。");
            return;
        }
        String[] str = name.split(" ");
        if (str.length != 3){
            System.out.println("格式不正确。");
            return;
        }
        String format = String.format("%s,%s.%c", str[2], str[0], str[1].toUpperCase().charAt(0));
        System.out.println(format);

    }

}

4.判断字符类型

charAt函数

toCharArray()函数

package com.homework13;


public class Homework04 {
    public static void main(String[] args) {
        count("ASAhha 11H");
    }
    public static void count(String str){
        if (str == null){
            System.out.println("不能为空。");
            return;
        }
        int counterNum = 0;
        int counterUp = 0;
        int counterLow = 0;
        int counterOther = 0
        char[] chars = str.toCharArray();//或是通过charAt()得到对应的字符
        for(int j = 0; j < chars.length; j++) {
            if (chars[j] >= '0' && chars[j] <= '9'){
                counterNum++;
            }else if (chars[j] >= 'A' && chars[j] <= 'Z'){
                counterUp++;
            }else if (chars[j] >= 'a' && chars[j] <= 'z'){
                counterLow++;
            } else{
                counterOther++;
            }
        }
        System.out.println("数字：" + counterNum +
                "n大写字母：" + counterUp +
                "n小写字母：" + counterLow);
    }
}

5.String内存分布

1.直接赋值，指向常量池；
2.创建字符串对象，对象中的value指向常量池，若常量池中存在对应的字符串，直接指向该字符串；

JAVA常用类作业（Chapter13）

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