java - 构建字符串避免重复的最佳方法

Question

我有一个将在 URL 中使用的硬编码字符串，我想知道构建这个字符串的最佳方法是什么，而不必重复单词 country, or, and, number?这是一个缩短的版本，因为 URL 中将包含更多国家和数字。

String url = "&filter=country='UK' or "
                      + "country='FR' or "
                      + "country='CA' or "
                      + "country='US' and "
                      + "number='123' and "
                      + "number='789'";

Answer 1

您可以结合使用 StringBuilder 和 String 格式来构建特定的 URL 参数化。

这是一个例子:

// test data
List<String> countries = Arrays.asList("UK", "FR","CA", "US");
List<String> numbers = Arrays.asList("123", "789");

// these can be compile-time constants
String disjunct  = " or ";
String conjunct = " and ";
String countryFormat = "country='%s'";
String numberFormat = "number='%s'";

// result 
StringBuilder result = new StringBuilder("&filter=");

// adding countries
for (String country: countries) {
    result.append(String.format(countryFormat, country)).append(disjunct);
}
// removing last "or"
result.delete(result.lastIndexOf(disjunct), result.length());

// adding first "and"
result.append(conjunct);

// adding numbers
for (String number: numbers) {
    result.append(String.format(numberFormat, number)).append(conjunct);
}
// removing last "and"
result.delete(result.lastIndexOf(conjunct), result.length());

// printing result
System.out.println(result);

输出

&filter=country='UK' or country='FR' or country='CA' or country='US' and number='123' and number='789'