当我运行代码时,我没有得到 setDepartment 方法 所需的结果。如果用户输入了错误的选择,我会试图诱骗他们。当我执行代码并输入一个毫无疑问应该执行的值(字符串)时,它不会执行。我已经测试过,看看问题出在哪里。唯一有效的是当我尝试将正确的值硬编码到方法中时。如果我输入了错误的值并捕获了用户,并且输入了正确的值,用户仍然被困在循环中。我检查了我的循环中是否有任何逻辑错误,但我找不到问题。我完全不知所措,我迫不及待地想找到我搞砸的地方。
请忽略courseCost实例变量我还没有处理过,请忽略department后面的system.out.println(department) =在setDepartment方法中的department.toUpperCase。我在 setDepartment 方法 中使用 system.out.println(department) 来排除 department=department.toUpperCase 上可能出现的任何错误 代码行。另外,你可以忽略其他一切,其他一切都很好。感谢您抽出宝贵时间查看。
import java.util.Scanner;
public class Course {
static Scanner keyboard = new Scanner(System.in);
private String department;
private int courseNumber;
private int courseCredits;
private double courseCost;
public Course () {
department = "unknown";
courseNumber = 0;
courseCost = 0;
courseCredits = 0;
}
public Course(String department, int courseNumber, int courseCredits) {
setDepartment(department);
setCourseNumber(courseNumber);
setCourseCredits(courseCredits);
//courseCost = no value will be passed to the constructor, courseCost will be calculated as courseCredits/2 * $500, see setter below (if the course is a Lab Course add $100 to the cost)
}
public String getDepartment() {
return department;
}
public int getCourseNumber() {
return courseNumber;
}
public int getCourseCredits() {
return courseCredits;
}
public double getCourseCost() {
return courseCost;
}
public void setDepartment(String department) {
boolean enteredCorrectly = false;
//department = department.toUpperCase();
do{
department = department.toUpperCase();
System.out.println(department);
//ENGL, MATH, COMP, HIST, HUMN, SCIE, LANG, PHYS
if( (department == "ENGL") || (department == "MATH") || (department == "COMP") ||
(department == "HIST") || (department == "HUMN") || (department == "SCIE") ||
(department == "LANG") || (department == "PHYS") ) {
this.department = department;
enteredCorrectly = true;
} else {
System.out.println("Please re-enter a valid department.");
department = keyboard.nextLine();
}
} while(!(enteredCorrectly));
}
public void setCourseNumber(int courseNumber) {
boolean enterCorrectly = false;
do{
if(1 <= courseNumber && courseNumber <= 399) {
this.courseNumber = courseNumber;
enterCorrectly = true;
} else {
System.out.println("Please re-enter a valid course number.");
courseNumber = keyboard.nextInt();
keyboard.nextLine();
}
} while(!(enterCorrectly));
}
public void setCourseCredits(int courseCredits) {
boolean enterCorrectly = false;
do{
if(courseCredits == 3 || courseCredits == 4 || courseCredits == 6) {
this.courseCredits = courseCredits;
enterCorrectly = true;
} else {
System.out.println("Please re-enter a valid course credits.");
courseCredits = keyboard.nextInt();
keyboard.nextLine();
}
} while(!(enterCorrectly));
}
public void setCourseCost(double courseCost) {
this.courseCost = courseCost;
}
public static void main(String[] args) {
Course c = new Course ("engl", 991, 1);
}
}
最佳答案
我认为它没有给你预期结果的原因是因为在比较 block 中你使用了运算符==
,这意味着你正在比较字符串的引用:
if( (department == "ENGL") || (department == "MATH") || (department == "COMP") ||
(department == "HIST") || (department == "HUMN") || (department == "SCIE") ||
(department == "LANG") || (department == "PHYS") ) {
this.department = department;
enteredCorrectly = true;
}
在Java中,要比较字符串的值,您应该使用.equals()
方法:
if( (department.equals("ENGL") || (department.equals("MATH") || (department.equals("COMP") ||
(department.equals("HIST") || (department.equals("HUMN") || (department.equals("SCIE") ||
(department.equals("LANG") || (department.equals("PHYS") ) {
this.department = department;
enteredCorrectly = true;
}
关于java - 为什么在没有语法错误或运行时错误的情况下这行代码不会执行,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/60586658/