如何在Java中使用String.format正确对齐? [英] How do I properly align using String.format in Java?

问题描述

比方说，我有几个变量，我想格式化它们，以便它们全部对齐，但是变量的长度不同.例如:

Let's say I have a couple variable and I want to format them so they're all aligned, but the variables are different lengths. For example:

String a = "abcdef";
String b = "abcdefhijk";

我也有价格.

double price = 4.56;

我怎么能格式化它，所以不管String多久，它们都以两种方式对齐?

How would I be able to format it so no matter how long the String is, they are aligned either way?

System.out.format("%5s %10.2f", a, price);
System.out.format("%5s %10.2f", b, price);

例如，上面的代码将输出如下内容:

For example, the code above would output something like this:

abcdef       4.56
abcdefhijk       4.56

但是我希望它输出如下内容:

But I want it to output something like this:

abcdef      4.56
abcdefhijk  4.56

我将如何去做?预先感谢.

How would I go about doing so? Thanks in advance.

推荐答案

使用固定大小格式:

使用固定大小的格式字符串可以将字符串打印在 具有固定大小的列的表格外观:

Using format strings with fixed size permits to print the strings in a table-like appearance with fixed size columns:

String rowsStrings[] = new String[] {"1", 
                                     "1234", 
                                     "1234567", 
                                     "123456789"};

String column1Format = "%-3.3s";  // fixed size 3 characters, left aligned
String column2Format = "%-8.8s";  // fixed size 8 characters, left aligned
String column3Format = "%6.6s";   // fixed size 6 characters, right aligned
String formatInfo = column1Format + " " + column2Format + " " + column3Format;

for(int i = 0; i < rowsStrings.length; i++) {
    System.out.format(formatInfo, rowsStrings[i], rowsStrings[i], rowsStrings[i]);
    System.out.println();
} 

输出:

1   1             1
123 1234       1234
123 1234567  123456
123 12345678 123456

在您的情况下，您可以找到要显示的字符串的最大长度，并使用该长度来创建适当的格式信息，例如:

In your case you could find the maximum length of the strings you want to display and use that to create the appropriate format information, for example:

// find the max length
int maxLength = Math.max(a.length(), b.length());

// add some space to separate the columns
int column1Length = maxLength + 2;

// compose the fixed size format for the first column
String column1Format = "%-" + column1Length + "." + column1Length + "s";

// second column format
String column2Format = "%10.2f";

// compose the complete format information
String formatInfo = column1Format + " " + column2Format;

System.out.format(formatInfo, a, price);
System.out.println();
System.out.format(formatInfo, b, price);

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