java练习题之String方法运用

应用知识点：String类

1：(String 类)仔细阅读以下代码段：

String s = "hello";

String t="hello";

char[] c = {'h','e','l','l','o'};

2：下列选项输出结果为false 的语句是()

System.out.println( s.euqals( t ) );

System.out.println( t.equals( c ) );

System.out.println( s==t );

System.out.println( t.equals( new String(c) ) );

System.out.println( t.equals( new String("hello")) );

3：(String 类)关于 java.lang.String 类，以下描述正确的一项是()(看源码)

String 类是 final 类故不可以继承。空间不可变吧

String 类是 final 类故可以继承。

String 类不是 final 类故不可以继承。

String 类不是 final 类故可以继承。

4：(String 类)应用程序的 main 方法中有以下语句，则输出的结果是

A. false B. true C. 1 D. 0

5：(String 类)已知String 对象s=”abcdefg”，则s.substring(2,5)的返回值为（）

A．”bcde” B．”cde” C．”cdef” D．”def”

6：(String 类)已知s 为一个String 对象，s=”abcdefg”，则s.charAt(1)的返回值为（）。

A．a B．b C．f D．g

7：接着实现昨天的题，定义一个person类，要求如下：

① 属性：身份证号,姓名,性别,年龄,户籍,出生日期（String类型,"1998-09-09"）

② 属性私有化，提供get/set,构造方法

③ 介绍格式：（toString）

姓名+户籍+年龄

④ 提供对象比较equals方法，只要身份证号+姓名相同就认为对象相等

⑤ 写一个测试类，定义一个Person数组，创建多个Person对象存储在数组中，

i. 打印输出所有Person对象的信息

ii. 用控制台输入一个Person信息：(注意：跟昨天的输入有区别！！！)

例如："370828199902145066-刘航-男-58-北京-1955/01/01"

判断数组中是否存在和此对象相等的对象(身份证号+姓名相同就认为对象相等)

iii. 判断Person数组中,名字是否有包含"胡"的联系人,有,打印信息.

iv. 任意输入一个姓 ,判断数组中是否存在有此姓的Person对象.

v.输出5月份出生的学生信息

package com.by.homework2;public class Person{private String idCard;private String name;private String sex;private int age;private String location;private String birthday;public Person() {}public Person(String idCard, String name, String sex, int age, String location, String birthday) {this.idCard = idCard;this.name = name;this.sex = sex;this.age = age;this.location = location;this.birthday = birthday;}public String getIdCard() {return idCard;}public void setIdCard(String idCard) {this.idCard = idCard;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getSex() {return sex;}public void setSex(String sex) {this.sex = sex;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}public String getLocation() {return location;}public void setLocation(String location) {this.location = location;}public String getBirthday() {return birthday;}public void setBirthday(String birthday) {this.birthday = birthday;}/* public String toString(){return "姓名:"+name+",户籍："+location+",年龄："+age;}*/@Overridepublic String toString() {return "姓名:"+name+",户籍："+location+",年龄："+age;}public boolean equals(Object o){if(this==o){return true;}if (this.getClass()!=o.getClass()||o.getClass()==null){return false;}Person person=(Person) o;return this.idCard.equals(person.idCard)&&this.name.equals(person.name);}
}package com.by.homework2;import java.util.Scanner;public class PersonTest {public static void main(String[] args) {Person[]people={new Person("1307262000","张三","男",18,"河北省","2000-01-01"),new Person("1307262001","李四","女",19,"河南省","2000-05-01"),new Person("1307262002","王五","男",20,"湖北省","2000-03-01"),new Person("123456789","胡麻子","男",21,"湖南","2000-11-11")};Scanner sc=new Scanner(System.in);for (int i = 0; i < people.length; i++) {System.out.println(people[i]);}//查询胡姓人boolean boo2=false;for (int i = 0; i < people.length; i++) {if(people[i].getName().indexOf("胡")==0){System.out.println("有胡姓叫："+people[i].getName());boo2=true;}}if(!boo2){System.out.println("没有胡姓人");}char[]chars;for (int i = 0; i < people.length; i++) {chars=people[i].getName().toCharArray();}/*for (int i = 0; i < chars.length; i++) {chars[0]}*///查询是否有该姓的名字System.out.println("任意输入一个姓，看是否有");String name1=sc.next();char []chars1=name1.toCharArray();String str3= String.valueOf(chars1[0]);boolean boo3=false;for (int i=0;i< people.length;i++){boolean boo4=people[i].getName().contains(str3);if (boo4){System.out.println("有姓名为：："+people[i]);boo3=true;}}if (!boo3){System.out.println("无相等的");}for (int i = 0; i < people.length; i++) {if(people[i].getBirthday().indexOf("5")==6){System.out.println(people[i]+"，生日为："+people[i].getBirthday());}}for (int i = 0; i < people.length; i++) {String str=String.valueOf(people[i].getBirthday().charAt(6));if(str.equals("5")){System.out.println(people[i]+"，生日为："+people[i].getBirthday());}}System.out.println("请输入身份证号");String idCard=sc.next();System.out.println("请输入姓名");String name=sc.next();System.out.println("请输入性别");String sex=sc.next();System.out.println("请输入年龄");int age=sc.nextInt();System.out.println("请输入籍贯");String location=sc.next();System.out.println("请输入出生日期");String birthday=sc.next();Person person=new Person(idCard,name,sex,age,location,birthday);String str=idCard+"-"+name+"-"+sex+"-"+age+"-"+location+"-"+birthday;System.out.println(str);String []str1=str.split("-");boolean boo1=false;for (int i = 0; i < people.length; i++) {if (str1[0].equals(people[i].getIdCard())&&str1[1].equals(people[i].getName())){System.out.println("相等");boo1=true;}}if (!boo1){System.out.println("不相等");}//输入一个完整的信息System.out.println("请输入信息");String infor=sc.next();String []strings=infor.split("-");Person person1=new Person(strings[0],strings[1],strings[2],Integer.parseInt(strings[3]),strings[4],strings[5]);boolean boo=false;for (int i = 0; i < people.length; i++) {if(person1.equals(people[i])){System.out.println("相等的为："+people[i]);boo=true;}}if(!boo){System.out.println("没有相等的");}}
}

8：获取“Wangxx@zparkhr.com.cn”中的用户名“Wangxx”

String s3="Wangxx@zparkhr.com.cn";
System.out.println(s3.substring(0,6));

9：验证“Wanxxj@zparkhr.com.cn”是否为一个合法邮箱

合法邮箱要求：

1、有“@”和“.”符号

2、“.”在“@”后面

package com.by.homework2;public class ContainAndIndexOf {public static void main(String[] args) {String str="Wanxxj@zparkhr.com.cn";if (str.contains("@")&&str.contains(".")){if (str.indexOf(".")>str.indexOf("@")){System.out.println(str+":是一个合法邮箱");}}}
}

10：控制台输入格式为“张三-18-男-3000.0”的字符串5个，解析为工人对象分别对应为名字，年龄，性别，工资的属性值，并存入工人数组

package com.by.homework2;import java.util.Scanner;public class Worker {private String name;private int age;private String sex;private double salary;public Worker() {}public Worker(String name, int age, String sex, double salary) {this.name = name;this.age = age;this.sex = sex;this.salary = salary;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}public String getSex() {return sex;}public void setSex(String sex) {this.sex = sex;}public double getSalary() {return salary;}public void setSalary(double salary) {this.salary = salary;}@Overridepublic String toString() {return "Worker{" +"name='" + name + '\'' +", age=" + age +", sex='" + sex + '\'' +", salary=" + salary +'}';}
}class WorkerTest{public static void main(String[] args) {Scanner sc=new Scanner(System.in);System.out.println("请输入员工信息");String str=sc.next();String []strings=str.split("-");String name = null;int age=0;String sex=null;double salary = 0;Worker worker1 = null;Worker worker2 = null;Worker worker3 = null;Worker worker4 = null;Worker worker5 = null;int num=0;//zhang-18-nan-1000-li-19-nan-2000-wang-20-nan-3000-zhao-21-nan-4000-qian-22-nan-5000for (int i=1;i<=5;i++) {name=strings[num];age=Integer.parseInt(strings[1+num]);sex=strings[2+num];salary=Double.parseDouble(strings[3+num]);System.out.println(name+age+sex+salary);if (i==1){worker1=new Worker(name,age,sex,salary);}if (i==2){worker2=new Worker(name,age,sex,salary);}if (i==3){worker3=new Worker(name,age,sex,salary);}if (i==4){worker4=new Worker(name,age,sex,salary);}if (i==5){worker5=new Worker(name,age,sex,salary);}
//            System.out.println();num+=4;}Worker[] workers={worker1,worker2,worker3,worker4,worker5};for (int i = 0; i < workers.length; i++) {System.out.println(workers[i].toString());}}
}

请输入员工信息

zhang-18-nan-1000-li-19-nan-2000-wang-20-nan-3000-zhao-21-nan-4000-qian-22-nan-5000

zhang18nan1000.0

li19nan2000.0

wang20nan3000.0

zhao21nan4000.0

qian22nan5000.0

Worker{name='zhang', age=18, sex='nan', salary=1000.0}

Worker{name='li', age=19, sex='nan', salary=2000.0}

Worker{name='wang', age=20, sex='nan', salary=3000.0}

Worker{name='zhao', age=21, sex='nan', salary=4000.0}

Worker{name='qian', age=22, sex='nan', salary=5000.0}

Process finished with exit code 0

11：银行系统需要登记用户的身份证号，为了防止用户输入身份证号的数位有误，我们应该使用什么方法？

.chatAt（17）！=0 && .charAt(17+) ==0

12：给定一个由数字组成的字符串

如:“376472364760183013010832“；

统计每个数字出现的次数

String s="376472364760183013010832";
byte[] s1=s.getBytes();
int sum=0;
for (int i = 0; i < s1.length; i++) {for (int j = 0; j <= s1.length-1; j++) {if(s1[i]==s1[i+1]){sum++;}}}System.out.println(s1[i]+"出现的次数是"+sum);}

13：将随机获取的UUID（含义是通用唯一识别码）中的“-”去掉。

提示：java.util.UUID.randomUUID().toString()//可以获取随机UUID

格式：e6c57443-1667-4d75-98f6-a8863d95e58f

package com.by.homework2;
import java.util.UUID;
public class Uuid {public static void main(String[] args) {String uuid=UUID.randomUUID().toString();System.out.println(uuid);String []str=uuid.split("-");for (int i = 0; i < str.length; i++) {System.out.print(str[i]);}}}

14:在给定字符串“ABDEFGabdefghijklmnMNKJ1234567"中随机获取4个字符，并使用随机获取的4个字符，使用StringBuilder拼接成字符串（随机获取到4个字符串中不可以出现重复字符,忽略大小写！如果当前随机内容已经出现，则重新随机本次）

提示：创建随机数对象java.util.Random.

java.util.Random r=new java.util.Random();

random.next(100);//可以获取到0-99中任意一个随机数。

获取到的随机数作为字符串的字符下标进行取值。

package com.by.homework2;import java.util.Random;public class RandomAppends {public static void main(String[] args) {String input = "ABDEFGabdefghijklmnMNKJ1234567";Random random = new Random();StringBuilder sb = new StringBuilder();while (sb.length() < 4) {int index = random.nextInt(input.length());char c = input.charAt(index);String str=String.valueOf(c);if (!sb.toString().contains(str)) {sb.append(c);}}System.out.println(sb.toString());}
}

15:将一个字符串进行反转。将字符串中指定部分进行反转。比如"abcdefg"，反转子串"cdef"，转为"abfedcg"

package com.by.homework2;import java.util.Scanner;public class Roolback {public static void main(String[] args) {Scanner scanner=new Scanner(System.in);System.out.println("请输入字符串");String str=scanner.next();System.out.println("反转其中内容");String str1=scanner.next();int num=str.indexOf(str1);char []chars=str.toCharArray();char a=0;char b=0;for (int i = 0; i < chars.length; i++) {if (i==num){a=chars[i];b=chars[i+1];chars[i]=chars[i+str1.length()-1];chars[i+1]=chars[i+str1.length()-2];chars[i+str1.length()-1]=a;chars[i+str1.length()-2]=b;}System.out.print(chars[i]);}/* String a="abcdefg";String b="edcb";char[]cs=b.toCharArray();String c="";for (int i = cs.length-1; i >=0; i--) {c+=cs[i];}System.out.println(a.replace(b,c));*/}
}

请输入字符串

abcdefg

反转其中内容

cdef

abfedcg

Process finished with exit code 0

16:使用方法判断字符串“zxcvbnmalskqpwoeiruty156789~!@#$%^&()”和字符串“!^#145agtkdbm”中字符重复的个数

package com.by.homework2;public class Test15 {public static void main(String[] args) {String str="zxcvbnmalskqpwoeiruty156789~!@#$%^&*()";String str1="!^#*145agtkdbm";char []c=str.toCharArray();char []c1=str1.toCharArray();int num=0;for (int i = 0; i < c.length; i++) {for (int i1 = 0; i1 < c1.length; i1++) {if (String.valueOf(c[i]).equals(String.valueOf(c1[i1]))){num++;}}}System.out.println(num);}
}

17:以下是一段歌词，请从这段歌词中统计出“朋友”出现的次数及每次的下标。

"这些年一个人，风也过，雨也走，有过泪，有过错, 还记得坚持甚么，真爱过才会懂，会寂寞会回首，终有梦终有你在心中。朋友一生一起走，那些日子不再有，一句话，一辈子，一生情，一杯酒。朋友不曾孤单过，一声朋友你会懂，还有伤，还有痛，还要走，还有我。";

package com.by.homework2;public class Test16 {public static void main(String[] args) {String str = "这些年一个人，风也过，雨也走，有过泪，有过错, 还记得坚持甚么，真爱过才会懂，会寂寞会回首，终有梦终有你在心中。朋友一生一起走，那些日子不再有，一句话，一辈子，一生情，一杯酒。朋友不曾孤单过，一声朋友你会懂，还有伤，还有痛，还要走，还有我。";int count = 0;int index = 0;while ((index = str.indexOf("朋友", index)) != -1) {count++;index++; // Move the index to the next character after "朋友"}System.out.println("朋友出现的次数: " + count);}
}

18:编写敏感词过滤程序
说明：在网络程序中，如聊天室、聊天软件等，经常需要对一些用户所提交的聊天内容中的敏感性词语进行过滤。如“性”、“色情”、“爆炸”、“恐怖”、“枪”、“军火”等，这些都不可以在网上进行传播，需要过滤掉或者用其他词语替换掉。

实现：让用户随机输入一段话，如果出现上述的敏感词汇，则用“***”对其进行替换

package com.by.homework2;import java.util.Scanner;public class Test17 {public static void main(String[] args) {Scanner sc=new Scanner(System.in);System.out.println("请输入一段话，我来输出");String str=sc.next();String []strings={"性","色情","爆炸","恐怖","枪","军火"};String str2="****";for (int i = 0; i < strings.length; i++) {if (str.contains(strings[i])){str.replace(strings[i],str2);System.out.println(str);}}

19:编写一个程序，设定一个有大小写字母的字符串，先将字符串的大写字符输出，再将字符串中的小写字符输出

package com.by.homework2;import java.util.Scanner;public class Test18 {public static void main(String[] args) {Scanner sc=new Scanner(System.in);System.out.println("请输入：");String str=sc.next();String str1;String str2;int num=0;byte[]bytes=str.getBytes();char []chars=new char[bytes.length];for (int i = 0; i < bytes.length; i++) {if(bytes[i]>=65&&bytes[i]<=90){chars[i]= (char) bytes[i];num++;}if(bytes[i]>=97&&bytes[i]<=122){chars[i+num]= (char) bytes[i];}}for (int j = 0; j < chars.length; j++) {System.out.print(chars[j]);}}
}