字符串未显示，打印“null”

Question

今天刚开始学习Java，所以请原谅我的业余错误。问题是它没有显示每个人最喜欢的颜色，而是显示“null”，我有 Pawn 的编码经验，所以我猜我没有正确创建字符串或者只是没有以某种方式填充它。

谢谢！

我试过这些代码，但我得到的是“null”，而不是每个人最喜欢的颜色。

import java.io.*;

public class Employee {

   String name;

   int age;

   String designation;

   String favoriteColor;

   double salary;

   // This is the constructor of the class Employee

   public Employee(String name) {

      this.name = name;

   }

   // Assign the age of the Employee  to the variable age.

   public void empAge(int empAge) {

      age = empAge;

   }

   /* Assign the designation to the variable designation.*/

   public void empDesignation(String empDesig) {

      designation = empDesig;

   }

   /* Assign the salary to the variable salary.*/

   public void empSalary(double empSalary) {

      salary = empSalary;

   }

   public void empFavoriteColor(String empColor) {

       favoriteColor = empColor;

   }

   /* Print the Employee details */

   public void printEmployee() {

      System.out.println("Name:"+ name );

      System.out.println("Age:" + age );

      System.out.println("Designation:" + designation );

      System.out.println("Salary:" + salary);

      System.out.println("Favorite color:" + favoriteColor);

   }

}

import java.io.*;

public class EmployeeTest {

   public static void main(String args[]) {

      /* Create two objects using constructor */

      Employee empOne = new Employee("James Smith");

      Employee empTwo = new Employee("Mary Anne");

      Employee empThree = new Employee("Alex Johnson");

      // Invoking methods for each object created

      empOne.empAge(26);

      empOne.empDesignation("Senior Software Engineer");

      empOne.empSalary(1000);

      empOne.printEmployee();

      empOne.empFavoriteColor("Green");

      empTwo.empAge(21);

      empTwo.empDesignation("Software Engineer");

      empTwo.empSalary(500);

      empTwo.printEmployee();

      empTwo.empFavoriteColor("Blue");

   }

}

Answer 1

您需要printEmployee();先致电empFavoriteColor()，如下所示：import java.io.*;public class EmployeeTest {   public static void main(String args[]) {      /* Create two objects using constructor */      Employee empOne = new Employee("James Smith");      Employee empTwo = new Employee("Mary Anne");      Employee empThree = new Employee("Alex Johnson");      // Invoking methods for each object created      empOne.empAge(26);      empOne.empDesignation("Senior Software Engineer");      empOne.empSalary(1000);      empOne.empFavoriteColor("Green");      empOne.printEmployee();      empTwo.empAge(21);      empTwo.empDesignation("Software Engineer");      empTwo.empSalary(500);      empTwo.empFavoriteColor("Blue");      empTwo.printEmployee();      empThree.empAge(16);      empThree.empDesignation("Software Developer" );      empThree.empSalary(250);      empThree.empFavoriteColor("Orange");      empThree.printEmployee();   }}

Answer 2

您在调用printEmployee()before empFavoriteColor()，因此打印时该字符串为 null 。