Java中日期类的字符串格式

Question

我有这个程序可以打印所需的format 中的数据。但我很难让它工作。

这是我的代码和输出：

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;

public class TestingStuff {

    public static void main(String[] args){
        Calendar calendar = Calendar.getInstance();
        calendar = new GregorianCalendar(2014, 07, 18);
        Date startDate = calendar.getTime();
        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("MM/dd/yy");
        String formatted = simpleDateFormat.format(startDate);
        String result="";
        String header2=String.format("%s %20s %20s %20s%n", "Account","Date","Hours","Skill");
        result+=header2;
        result+="-----------------------------------------------------------------------\n";
        result+=String.format("summary %20s%n",formatted);
        result+=String.format("Totabl Billable: %25s%n", 40);
        result+=String.format("Total Non-Billable: %25s%n", 0);
        result+=String.format("Total Hours %25s%n", 40);
        System.out.println(result);

    }

}

输出：

Account                 Date                Hours                Skill
-----------------------------------------------------------------------
summary             08/18/14
Totabl Billable:                        40
Total Non-Billable:                         0
Total Hours                        40

预期输出：

    Account                 Date                Hours                Skill
    -----------------------------------------------------------------------
    summary                08/18/14
    Totabl Billable:                              40
    Total Non-Billable:                            0
    Total Hours                                   40

如您所见，这些数字并未相对于选项卡标题居中。我还在硬编码spaces 的数量，例如（%20s），我认为这不是正确的方法。有没有办法告诉 使用居中自动格式化？

Answer 1

我建议对左对齐使用 java.util.Formatter '-' 标志。来自 Javadoc：

'-' '\u002d' 左对齐输出。空格 ('\u0020') 将根据需要添加到转换值的末尾以填充字段的最小宽度。

所以，如果我们将此应用于您的示例：

public static void main(String[] args) {
    Calendar calendar = Calendar.getInstance();
    calendar = new GregorianCalendar(2014, 07, 18);
    Date startDate = calendar.getTime();
    SimpleDateFormat simpleDateFormat = new SimpleDateFormat("MM/dd/yy");
    String formatted = simpleDateFormat.format(startDate);
    String result = "";
    String header2 = String.format("%s %20s %20s %20s%n", "Account", "Date", "Hours", "Skill");
    result += header2;
    result += "-----------------------------------------------------------------------\n";
    result += String.format("summary %20s%n", formatted);
    result += String.format("%-40s %4d%n", "Totabl Billable:", 40);
    result += String.format("%-40s %4d%n", "Total Non-Billable:", 0);
    result += String.format("%-40s %4d%n", "Total Hours:", 40);
    System.out.println(result);
}

将用空格填充第一个输入（行标签）以匹配固定宽度（在本例中为 40）。这将产生：

Account                 Date                Hours                Skill
-----------------------------------------------------------------------
summary             08/18/14
Totabl Billable:                           40
Total Non-Billable:                         0
Total Hours                                40

这为动态行标签提供了额外的好处，因为它会自动填充到指定的宽度，而不管标签的长度如何。它会比尝试计算每个可能的标签的空间更灵活。

Answer 2

        String header2=String.format("%s\t\t\t%s\t\t\t%s\t\t\t%s\n", "Account","Date","Hours","Skill");
        result+=header2;
        result+="-------------------------------------------------------------------------------\n";
        result+=String.format("summary \t\t%s\n",formatted);
        result+=String.format("Totabl Billable: \t\t\t\t%s\n", 40);
        result+=String.format("Total Non-Billable: \t\t\t\t%s\n", 0);
        result+=String.format("Total Hours \t\t\t\t\t%s\n", 40);
        System.out.println(result);

这应该工作。即使我输入不同的数字也为我工作。