像表格一样格式化 Java 输出

我试图以类似表格的格式输出有关我的程序存储的学生的信息，因为 \t 并不总是提供正确的间距。为了做到这一点，我遇到了这个问题 https://stackoverflow.com/a/2745239/1692226并尝试启用类似的解决方案。但是，当我尝试这样执行代码时，我在代码中的格式行中遇到了错误。

public void displayStudents (){
    System.out.println ("\n-----------------------------");
    System.out.println ("Email System - Display Students");
    System.out.println ("-----------------------------");
    System.out.format("%10s%15d%15s%15s%20s", "Grade", "Last Name", "First Name", "Student Number", "Parent Email");

    StudentNode current = top;
    while (current != null){
        Student read = current.getStudentNode();
        System.out.format ("%10s%15d%15s%15s%20s", ""+read.getClass(), read.getLastName(), read.getFirstName(), ""+read.getStudentNum(), read.getParentEmail());
        //This will output with a set number of character spaces per field, giving the list a table-like quality
    }
}//End of displayStudents

The goal of the code is to output in a manner similar to the following image.

请帮助我找出我的错误。也许有另一种方法可以执行此操作吗？

Thanks.

编辑：我收到的错误是

GradeException in thread "main" java.util.IllegalFormatConversionException: d != java.lang.String
at java.util.Formatter$FormatSpecifier.failConversion(Unknown Source)
at java.util.Formatter$FormatSpecifier.printInteger(Unknown Source)
at java.util.Formatter$FormatSpecifier.print(Unknown Source)
at java.util.Formatter.format(Unknown Source)
at java.io.PrintStream.format(Unknown Source)
at StudentList.displayStudents(StudentList.java:184)
at OnlineCommunications.emailOption(OnlineCommunications.java:403)
at OnlineCommunications.main(OnlineCommunications.java:451)

需要注意的是，Grade 是整数，Long 是双精度数。

错误是因为%d用于数字非浮点值（int, long, etc).

在打印标题的行中，您必须使用%XXs（其中 XX 是数字）因为您通过了Strings 作为参数：

System.out.format("%10s%15s%15s%15s%20s",
    "Grade", "Last Name", "First Name", "Student Number", "Parent Email");

在里面的行中while-loop，你需要设置%d为了int and long变量，例如年级和学号，无需将其转换为String using "" + intProperty:

System.out.format ("%10d%15s%15s%15d%20s",
    read.getClass(), read.getLastName(), read.getFirstName(),
    read.getStudentNum(), read.getParentEmail());

由于您似乎想要将输出格式化为左侧（而不是右侧），因此您应该在 XX 数字之前添加一个连字符 (-)：

//similar for title
System.out.format ("%-10d%-15s%-15s%-15d%-20s",
    read.getClass(), read.getLastName(), read.getFirstName(),
    read.getStudentNum(), read.getParentEmail());

注意：我假设read.getClass() and read.getStudentNum()将返回Grade and Student number值作为int or long.