我无法在循环中增加studentid的值。

huangapple
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英文:

I can not increase the studentid value in For

问题

我正在使用Java进行一些编码，但它不起作用：

  1. import java.util.Scanner;
  2. import java.util.Arrays;
  4. public class Main {
  5.     public static void main(String[] args) {
  6.         Scanner input = new Scanner(System.in);
  7.         String[] studentId = new String[3];
  8.         Student name;
  10.         for (int i = 0; i < 3; i++) {
  11.             System.out.print("输入姓名 => ");
  12.             name = new Student(input.next());
  13.             studentId[i] = name.toString();
  14.         }
  16.         for (int i = 0; i < 3; i++) {
  17.             System.out.println(studentId[i]);
  18.         }
  19.     }
  20. }
  22. public class Student {
  23.     private static int studentId;
  24.     private String name;
  26.     public Student(String name) {
  27.         this.name = name;
  28.         setStudentId(studentId++);
  29.     }
  31.     public int getStudentId() {
  32.         return studentId;
  33.     }
  35.     public void setStudentId(int studentId) {
  36.         this.studentId = studentId;
  37.     }
  39.     @Override
  40.     public String toString() {
  41.         return (this.studentId + " " + "学生是" + " " + "(" + this.studentId + ")" + this.name);
  42.     }
  43. }

我需要在创建新条目时自动增加ID。
我尝试了各种方法，但仍然无法使其递增。

英文:

I am doing some coding in Java, but it doesn't work:

import java.util.Scanner;

import java.util.Arrays;

public class Main
{

  1. 	public static void main(String[] args) 
  2. {
  3. Scanner input = new Scanner(System.in);
  4. String [] studentId = new String [3];
  5. Student name;
  6. for (int i = 0; i &lt; 3; i++) 
  7. {
  8. System.out.print(&quot;Enter Name =&gt; &quot;);
  9. name = new Student(input.next());
  10. studentId[i] = name.toString();
  11. }
  12. for (int i = 0; i &lt; 3; i++) 
  13. {
  14. System.out.println(studentId[i]);
  15. }    
  16. }
  17. }
  1. public class Student
  2. {
  3. private static int studentId;
  4. private String name;
  5. public Student(String name) 
  6. {
  7. this.name=name;    
  8. setStudentId(studentId++);
  9. }
  10. public int getStudentId() 
  11. {
  12. return studentId;
  13. }
  14. public void setStudentId(int studentId) 
  15. {
  16. this.studentId = studentId;
  17. }
  18. @Override
  19. public String toString()
  20. {
  21. return (this.studentId +&quot; &quot;+ &quot;student is &quot;+ &quot; &quot; + &quot;(&quot; + this.studentId + &quot;)&quot;+ this.name);
  22. }
  23. }

I need to auto-increment the Id when a new entry is created.
I try everything but still cant increased it.

答案1

得分: 1

你正在为所有人的ID使用静态变量。你需要一个单独的、非静态字段来存储每个个体的ID。

  1. public class Student
  2. {
  3.     private static int nextAvailableStudentId = 1;
  4.     private String name;
  5.     private int studentId;
  7.     public Student(String name) 
  8.     {
  9.         this.name = name;    
  10.         setStudentId(nextAvailableStudentId++);
  11.     }
  13.     public int getStudentId() 
  14.     {
  15.         return studentId;
  16.     }
  18.     public void setStudentId(int studentId) 
  19.     {
  20.         this.studentId = studentId;
  21.     }
  23.     @Override
  24.     public String toString()
  25.     {
  26.         return (this.studentId + " " + "student is " + " " + "(" + this.studentId + ")" + this.name);
  27.     }
  28. }
英文:

You are using a static variable for everyone's Ids. You need a separate, non-static field to store each individual Id.

  1. public class Student
  2. {
  3. private static int nextAvailableStudentId = 1;
  4. private String name;
  5. private int studentId;
  6. public Student(String name) 
  7. {
  8. this.name=name;    
  9. setStudentId(nextAvailableStudentId++);
  10. }
  11. public int getStudentId() 
  12. {
  13. return studentId;
  14. }
  15. public void setStudentId(int studentId) 
  16. {
  17. this.studentId = studentId;
  18. }
  19. @Override
  20. public String toString()
  21. {
  22. return (this.studentId +&quot; &quot;+ &quot;student is &quot;+ &quot; &quot; + &quot;(&quot; + this.studentId + &quot;)&quot;+ this.name);
  23. }
  24. }

答案2

得分: -1

在构造函数中应该是：

  1. {
  2. public Student(String name) 
  3. {
  4. this.name=name;    
  5. setStudentId(studentId + 1);
  6. }
  7. }
英文:

In constructor it should be:

  1. {
  2. public Student(String name) 
  3. {
  4. this.name=name;    
  5. setStudentId(studentId + 1);
  6. }
  7. }

huangapple
  • 本文由 发表于 2020年4月4日 01:30:07
  • 转载请务必保留本文链接：https://go.coder-hub.com/61017321.html
  • arrays
  • auto-increment
  • for-loop
  • java
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