java对txt的增删改查_用JAVA实现对txt文件文本增删改查

不念不忘少年蓝@ 2022-11-03 11:38 236阅读 0赞

packagecom.qiqiao.test;importjava.io.File;importjava.io.FileInputStream;importjava.io.FileOutputStream;importjava.io.ObjectInputStream;importjava.io.ObjectOutputStream;importjava.io.Serializable;importjava.util.Arrays;importjava.util.HashMap;importjava.util.HashSet;importjava.util.Scanner;importjava.util.Set;public classStudentManager \{private static File DB = new File("students.db");private static Set studentList = null;

@SuppressWarnings("unchecked")private static voidinitStudentList() \{if(DB.exists()) \{

FileInputStream fi= null;

ObjectInputStream oi= null;try\{

fi= newFileInputStream(DB);

oi= newObjectInputStream(fi);

Object obj=oi.readObject();

fi.close();

oi.close();if (obj instanceofSet)

studentList= (Set) obj;

\}catch(Exception e) \{

e.printStackTrace();

\}if (studentList == null)

studentList= new HashSet();

\}private static voidsave() \{if (studentList == null)return;if (!DB.exists())try\{

DB.createNewFile();

\}catch(Exception e) \{

e.printStackTrace();

FileOutputStream fo;try\{

fo= newFileOutputStream(DB);

ObjectOutputStream oo= newObjectOutputStream(fo);

oo.writeObject(studentList);

fo.close();

oo.close();

\}catch(Exception e) \{

e.printStackTrace();

\}private static Student\[\] getStudents(intid, String name) \{

HashSet rlt = new HashSet();if (id != 0) \{for(Student s : studentList) \{if (s.id ==id)

rlt.add(s);

\}else if (name != null && !name.isEmpty()) \{for(Student s : studentList) \{if(s.\_name.equalsIgnoreCase(name))

rlt.add(s);

\}return rlt.toArray(new Student\[0\]);

\}static\{

initStudentList();

\}static voidout(Object obj) \{

System.out.println(obj);

\}public static voidmenu() \{

out("Welcome to use Student Manager!\\n1-search student;\\t2-add student;\\t3-list all students;\\nothers-exit");

Scanner in= newScanner(System.in);

Student student= null;

String input=in.nextLine();if (input.equals("1")) \{

Student\[\] students= new Student\[0\];

out("please input name/id");

String ins=in.nextLine();if (ins.matches("\\\\d+"))

students= getStudents(Integer.parseInt(ins), null);elsestudents= getStudents(0, ins);if (students.length != 0) \{

out(Arrays.toString(students).replaceAll("\\\\\[|\\\\\]|, ", "\\n"));if (students.length == 1)

student= students\[0\];else\{

out("please choose a student by id:\\n");int i =in.nextInt();for(Student s : students) \{if (s.id ==i) \{

student=s;break;

\}else\{

out("error");

menu();

out("1-set score;\\t2-delete score;\\t3-delete student;\\tother-exit");int input1 =in.nextInt();

in.nextLine();

String course= null;float score = 0;switch(input1) \{case 1:

out("please input course");

course=in.nextLine();

out("please input score");

score=in.nextFloat();

in.nextLine();

student.setScore(course, score);break;case 2:

out("please input course");

course=in.nextLine();

student.removeScore(course);break;case 3:

student.removeFrom(studentList);break;

\}else\{

out("NO current record!");

\}if (input.equals("2")) \{

out("please input id");int id =in.nextInt();

in.nextLine();

out("please input name");

String name=in.nextLine();

out("please input class");

String cname=in.nextLine();

student= newStudent(id, name, cname);if(studentList.add(student)) \{

out("create success!\\n");

String input2= "-";while (!input2.isEmpty()) \{

out("set score? \\n1-yes;\\t2-no");

input2=in.nextLine();if (input2.equals("1")) \{

out("please input course");

String course=in.nextLine();

out("please input score");float score =in.nextFloat();

student.setScore(course, score);

in.nextLine();

\}else

break;

\}elseout("Error: id or student exists");

\}if (input.equals("3")) \{

out(studentList.toString().replaceAll("\\\\\[|\\\\\]|, ", "\\n"));

\}if(input.isEmpty())return;

save();

menu();

\}public static voidmain(String\[\] args) \{

menu();

\}class Student implementsSerializable \{publicString toString() \{return "id: "

\+id+ "\\tclass: "

\+\_class+ "\\tname: "

\+\_name+ courses.toString().replaceAll("\\\\\{|\\\\\}|, ", "\\n").replaceAll("=", ": ");

Student(intid, String \_name, String \_class) \{this.id =id;this.\_class =\_class;this.\_name =\_name;

\}private static final long serialVersionUID = 1L;public int id = 0;public String \_name = "";public String \_class = "";

HashMap courses = new HashMap();void setScore(String course, floatscore) \{

courses.put(course, score);

System.out.println("set success!\\n\\n" + this);

\}voidremoveScore(String course) \{

courses.remove(course);

System.out.println("delete success!\\n\\n" + this);

\};void removeFrom(Set>list) \{

list.remove(this);

System.out.println("delete success!");

\}public inthashCode() \{return 31;

\}public booleanequals(Object obj) \{

Student s= null;if (obj instanceofStudent) \{

System.out.println(1);

s=(Student) obj;return s.id ==id|| (s.\_class.equals(\_class) &&s.\_name.equals(\_name));

\}return false;

\}classDaJiangYou \{

DaJiangYou() \{

System.out.println("I am da jiang you");

java对txt的增删改查_用JAVA实现对txt文件文本增删改查

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