Question

我正在尝试创建一个控制台程序，允许您查看所有学生及其信息的列表，并使用指定的条目搜索列表。我目前正在处理您可以输入学生ID的部分，并且将显示匹配结果。问题是每当我使用ID选项作为输入时，do-while循环两次而不是一次。这很烦人，因为它会打印“CONSOLE＆gt;”消息两次。

我的示例输入是“20180001”

控制台上更具体的输入/输出：

Loop no: 0
CONSOLE>find
FIND >id
FIND ID >20180001
|   ID: 20180001    |    Name: Smith, John  |    Course: IT |    Year: 1st Year     |    Age: 18    |
Loop no: 1
CONSOLE>Loop no: 2
CONSOLE>

我的预期输出：

Loop no: 0
CONSOLE>find
FIND >id
FIND ID >20180001
|   ID: 20180001    |    Name: Smith, John  |    Course: IT |    Year: 1st Year     |    Age: 18    |
Loop no: 1
CONSOLE>

此处发生错误：

do {
            System.out.println("Loop no: " + temp);
            System.out.print("CONSOLE>");
            input = Scanner.nextLine();

主要课程

public class Main {
    public static void main(String[] args) throws InterruptedException {
        String input = "";
        int input2 = 0;
        Student s0 = new Student();
        Student s1 = new Student();
        Student s2 = new Student();
        Student s3 = new Student();
        Student s4 = new Student();
        Scanner Scanner = new Scanner(System.in);
        int temp = 0;

        fillStudents(s0, s1, s2, s3, s4);

        do {
            System.out.println("Loop no: " + temp);
            System.out.print("CONSOLE>");
            input = Scanner.nextLine();
            if (input.toUpperCase().equals("LIST STUDENTS")) {
                Student201.listStudents(s0, s1, s2, s3, s4);
            } /* else System.out.println("ERROR MESSAGE: '" + input + "' is not recognized "
                    + "as a command."); */
            if (input.toUpperCase().equals("FIND")) {
                System.out.print("FIND >");
                input = Scanner.nextLine();
                if (input.toUpperCase().equals("ID")) {
                    System.out.print("FIND ID >");
                    input2 = Scanner.nextInt();
                    if(s0.getStudentID() == input2) {
                        System.out.println(s0);
                    } /* else System.out.println("CONSOLE MESSAGE: No results were found with the first name '"
                            + input + "'."); */
                    if(s1.getStudentID() == input2) {
                        System.out.println(s1);
                    }
                    if(s2.getStudentID() == input2) {
                        System.out.println(s2);
                    }
                    if(s3.getStudentID() == input2) {
                        System.out.println(s3);
                    }
                    if(s4.getStudentID() == input2) {
                        System.out.println(s4);
                    }
                }
                if (input.toUpperCase().equals("FIRST NAME")) { // If the user chooses FIRST NAME to find students
                    System.out.print("FIND FIRST NAME >");
                    input = Scanner.nextLine();
                    if(s0.getFirstName().toUpperCase().equals(input.toUpperCase())) {
                        System.out.println(s0);
                    } /* else System.out.println("CONSOLE MESSAGE: No results were found with the first name '"
                            + input + "'."); */
                    if(s1.getFirstName().toUpperCase().equals(input.toUpperCase())) {
                        System.out.println(s1);
                    }
                    if(s2.getFirstName().toUpperCase().equals(input.toUpperCase())) {
                        System.out.println(s2);
                    }
                    if(s3.getFirstName().toUpperCase().equals(input.toUpperCase())) {
                        System.out.println(s3);
                    }
                    if(s4.getFirstName().toUpperCase().equals(input.toUpperCase())) {
                        System.out.println(s4);
                    }
                }
                if (input.toUpperCase().equals("LAST NAME")) { // If the user chooses LAST NAME to find students
                    System.out.print("FIND LAST NAME >");
                    input = Scanner.nextLine();
                    if(s0.getLastName().toUpperCase().equals(input.toUpperCase())) {
                        System.out.println(s0);
                    } /* else System.out.println("CONSOLE MESSAGE: No results were found with the last name '"
                            + input + "'."); */
                    if(s1.getLastName().toUpperCase().equals(input.toUpperCase())) {
                        System.out.println(s1);
                    }
                    if(s2.getLastName().toUpperCase().equals(input.toUpperCase())) {
                        System.out.println(s2);
                    }
                    if(s3.getLastName().toUpperCase().equals(input.toUpperCase())) {
                        System.out.println(s3);
                    }
                    if(s4.getLastName().toUpperCase().equals(input.toUpperCase())) {
                        System.out.println(s4);
                    }
                }

            }
        temp++;
        }while (!input.equals("exit"));

    }

    public static void fillStudents(Student s0, Student s1, Student s2, Student s3, Student s4) throws InterruptedException {

        clear();
        System.out.println("Filling the information of Students...");
        TimeUnit.SECONDS.sleep(1);
        clear();

        s0.setLastName("Smith");
        s0.setFirstName("John");
        s0.setAge(18);
        s0.setCourse("IT");
        s0.setYear("1st Year");
        s0.setStudentID(20180001);

        s1.setLastName("Wallace");
        s1.setFirstName("Mark");
        s1.setAge(18);
        s1.setCourse("IT");
        s1.setYear("1st Year");
        s1.setStudentID(20180002);

        s2.setLastName("Reese");
        s2.setFirstName("Tony");
        s2.setAge(18);
        s2.setCourse("MA");
        s2.setYear("1st Year");
        s2.setStudentID(20180003);

        s3.setLastName("Johnson");
        s3.setFirstName("Liza");
        s3.setAge(18);
        s3.setCourse("BA");
        s3.setYear("1st Year");
        s3.setStudentID(20180004);

        s4.setLastName("Nguyen");
        s4.setFirstName("Kim");
        s4.setAge(17);
        s4.setCourse("ECE");
        s4.setYear("1st Year");
        s4.setStudentID(20180005);
    }

    public static void clear() {
        for(int x = 0; x<=100; x++) {
            System.out.println();
        }
    }

}

学生班

package studentdirectory;

public class Student extends Student201{

    private String lastName;
    private String firstName;
    private String course;
    private String year;
    private int age;
    private int studentID;

    public String getLastName() {
        return lastName;
    }
    public void setLastName(String lastName) {
        this.lastName = lastName;
    }
    public String getFirstName() {
        return firstName;
    }
    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }
    public String getCourse() {
        return course;
    }
    public void setCourse(String course) {
        this.course = course;
    }
    public String getYear() {
        return year;
    }
    public void setYear(String year) {
        this.year = year;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public int getStudentID() {
        return studentID;
    }
    public void setStudentID(int studentID) {
        this.studentID = studentID;
    }
    @Override
    public String toString() {
        return "|\tID: " + this.getStudentID() + "\t|\t Name: " + this.getLastName() + ", "
                + this.getFirstName() + "\t|\t Course: " + this.getCourse() + "\t|\t Year: " +
                this.getYear() + "\t\t|\t Age: " + this.getAge() + "\t|";
    }

}

Student201班

package studentdirectory;

public class Student201{
    public static void listStudents(Student s0, Student s1, Student s2, Student s3, Student s4) {
        System.out.println(s0);
        System.out.println(s1);
        System.out.println(s2);
        System.out.println(s3);
        System.out.println(s4);
    }
}

Answer 1

最后，提出了解决方案。首先问题不在于输入问题在于loop do while循环首先执行语句，然后检查condition。我做的是我创建了一个infinite loop然后接受输入，输入之后我放了condition，如果input退出则会打破loop。< / p>

像这样的东西

while (true){       
        input = Scanner.nextLine();
        if(input.toUpperCase().equals("EXIT"))
        {
            break;
        }
        else
        {
          // Put the whole logic inside this
        }

你必须这样做，否则即使输入为exit，循环也会自动执行一次。

希望有帮助

Answer 2

我通过放置＆＃34; Scanner.nextLine（）;＆＃34;紧随＆＃34; Scanner.nextInt（）;＆＃34;。这阻止了它跳过input = Scanner.nextLine（）;

Scanner.nextInt（）;接受两个输入（我认为）

2 个答案: