如何正确使用 Switch-Case？

Question

首先，我很抱歉我的英语不好。 :< 我在一个小型 Java 项目中工作。我试图创建一个程序来管理学生名单。有两个 class。

学生class

import java.util.Scanner;

public class Student {

String rollNo;
String name;
int age;
String address;
float tMark;
float eMark;

public String getRollNo() {
    return rollNo;
}

public void setRollNo(String rollNo) {
    this.rollNo = rollNo;
}

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 getAddress() {
    return address;
}

public void setAddress(String address) {
    this.address = address;
}

public float gettMark() {
    return tMark;
}

public void settMark(float tMark) {
    this.tMark = tMark;
}

public float geteMark() {
    return eMark;
}

public void seteMark(float eMark) {
    this.eMark = eMark;
}

public void EnterInfo() {
    Scanner in = new Scanner(System.in);
    System.out.println("\nEnter the number: ");
    setRollNo(in.nextLine());
    System.out.println("Enter the name: ");
    setName(in.nextLine());
    System.out.println("Enter the age: ");
    setAge(in.nextInt());
    System.out.println("Enter the address: ");
    setAddress(in.nextLine());
    System.out.println("Enter the Theory mark: ");
    settMark(in.nextFloat());
    System.out.println("Enter the Exam mark: ");
    seteMark(in.nextFloat());
    System.out.println("\n");

}

public void UpdateInfo() {
    Scanner update = new Scanner(System.in);
    int choice = 0;
    boolean loop = false;
        System.out.println("Select a field to update: ");
        System.out.println("1. Number: " + getRollNo());
        System.out.println("2. Name: " + getName());
        System.out.println("3. Age: " + getAge());
        System.out.println("4. Address: " + getAddress());
        System.out.println("5. Theory mark: " + gettMark());
        System.out.println("6. Exam mark: " + geteMark());
        choice = update.nextInt();


        switch (choice) {
        case 1:
            System.out.println("New number: ");
            setRollNo(update.nextLine());
            break;
        case 2:
            {System.out.println("New name: ");
            setName(update.nextLine());}
        case 3:
            {System.out.println("New age: ");
            setAge(update.nextInt());}
        case 4:
            {System.out.println("New address: ");
            setAddress(update.nextLine());}
        case 5:
            {System.out.println("New Theory mark: ");
            settMark(update.nextFloat());}
        case 6:
            {System.out.println("New Exam mark: ");
            seteMark(update.nextFloat());}
        case 7:
            System.out.println("Do you want to continue updating? (1.Yes/2.No): ");
            int cont = update.nextInt();
            if (cont==1) {loop = true;} else {loop=false;}
            while (loop=true) {UpdateInfo();}
            break;

        }





}

public void StudentInfo() {
    System.out.println("===\nNo.: " + getRollNo() + "\nName: " + getName()
            + "\nAge: " + getAge() + "\nAddress: " + getAddress()
            + "\nT.Mark: " + gettMark() + "\nE.Mark: " + geteMark()
            + "\n===");
}

}

和 MainClass（用于测试目的）

public class MainClass {

public void showMenu() {
    System.out.println("1. Enter the students info.");
    System.out.println("2. Show list of student.");
    System.out.println("3. Find info.");
    System.out.println("4. Update info");
    System.out.println("5. Exit!");

}

public static void main(String[] args) {
    // TODO Auto-generated method stub
    Student std = new Student();
    std.UpdateInfo();
}

}

不幸的是，我的程序终于出错了。 :( 我无法用我的英语解释这个问题。但总的来说，我无法更新变量中的内容，UpdateInfo() 中的循环仍然运行并且无法停止。什么问题？我该如何解决？ :(

Answer 1

你是运行循环中的递归。如果您弄清楚此行块的含义......您已经解决了您的问题。选择一个或另一个...递归或循环。

int cont = update.nextInt();
if (cont==1) {loop = true;} else {loop=false;}
while (loop=true) {UpdateInfo();}
break;

如何正确使用 Switch-Case？

How can I use the Switch-Case in the right way?

java

switch-statement