格式化Java输出像表格一样 [英] Formatting Java Output Like a Table

问题描述

我试图以表格式的格式输出关于我的程序存储的学生信息，因为\并不总是提供正确的间隔。为了这样做，我遇到了这个问题，并试图启用类似的解决方案。然而，当我试图执行它的时候，我得到了代码中的格式行错误。

pre $ public void displayStudents ）{
System.out.println（\\\
-----------------------------）;
System.out.println（电子邮件系统 - 显示学生）;
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（））;
//这将输出每个字段的字符空间的数量，给列表一个类似于表格的质量
}
} //结束显示学生

代码的目标是以类似于以下图像的方式输出。

请帮助我找到我的错误。有没有可能的方法来执行此？

谢谢。

编辑：错误得到的是

 线程main中的GradeException java.util.IllegalFormatConversionException：d！= java.lang.String 
在java.util.Formatter $ FormatSpecifier.failConversion（未知源）
在java.util.Formatter $ FormatSpecifier.printInteger（未知源）
在java.util.Formatter $ FormatSpecifier.print（Unknown Source ）
在java.util.Formatter.format（未知源）
在java.io.PrintStream.format（未知源）
在StudentList.displayStudents（StudentList.java:184）$ b （OnlineCommunications.java:403）$ b $在OnlineCommunications.main（OnlineCommunications.java:451）
  

应该注意的是，Grade是一个整数，Long是一个double。

解决方案

因为％d 是数值非浮点值（ int ， long 等）。

在打印标题的行中，您必须使用％XXs （其中XX是数字），因为您正在传递 String s作为参数：

  System.out.format（％10s％15s％15s％15s％20s ，
年级，姓氏，名字，学生号码，家长电子邮件）; 
  

在 while循环 ，你需要为 int 和 long ％d >变量，例如Grade和Student Number，不需要使用+ intProperty ：转换为 / b>



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

由于它看起来像要将输出格式化为左侧（而不是右侧）你应该在XX号码之前加一个（ - ）符号：



  //类似于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（）和 read.getStudentNum（）会返回成绩和学号的值为 int 或 long 。

I am attempting to output information regarding students stored by my program in a tabular-like format as \t does not always provide the correct spacing. In order to do so, I came across this question and have attempted to enable a similar solution. However, I am obtaining errors with the format lines in my code when I attempt to execute it as such.

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.

Please aid me in finding my error. Is there perhaps an alternatively method to perform this?

Thanks.

EDIT: The error(s) I am getting are

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)

It should be noted that Grade is an integer and Long is a double.

解决方案

The error is because%d is for numeric non-floating point values (int, long, etc).

In the line where you print the titles, you have to use %XXs (where XX is a number) since you're passing Strings as parameters:

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

In the line inside the while-loop, you need to set %d for the int and long variables, like Grade and Student Number, there's no need to convert it to String using "" + intProperty:

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

Since it looks like you want to format the output to the left (and not to the right), you should add a hypen (-) symbol before the XX number:

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

Note: I assumed read.getClass() and read.getStudentNum() would return the Grade and Student number values as int or long.

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