在Python中,格式化字符串时,我可以按名称而不是按位置填充占位符,如下所示:

print "There's an incorrect value '%(value)s' in column # %(column)d" % \
  { 'value': x, 'column': y }

我想知道这在Java中是否可能(希望没有外部库)?


当前回答

另一个Apache Common StringSubstitutor的简单命名占位符的例子。

String template = "Welcome to {theWorld}. My name is {myName}.";

Map<String, String> values = new HashMap<>();
values.put("theWorld", "Stackoverflow");
values.put("myName", "Thanos");

String message = StringSubstitutor.replace(template, values, "{", "}");

System.out.println(message);

// Welcome to Stackoverflow. My name is Thanos.

其他回答

Apache Commons Lang的replaceEach方法可能会根据您的特定需求派上用场。你可以简单地用这个方法调用来替换占位符:

StringUtils.replaceEach("There's an incorrect value '%(value)' in column # %(column)",
            new String[] { "%(value)", "%(column)" }, new String[] { x, y });

给定一些输入文本,这将用第二个字符串数组中的相应值替换第一个字符串数组中出现的所有占位符。

试试Freemarker,模板库。

不完全是,但你可以使用MessageFormat多次引用一个值:

MessageFormat.format("There's an incorrect value \"{0}\" in column # {1}", x, y);

上面的事情也可以用string .format()来完成,但是如果你需要构建复杂的表达式,我发现messageFormat语法更干净,而且你不需要关心你放入字符串中的对象的类型

你可以在字符串助手类上有这样的东西

/**
 * An interpreter for strings with named placeholders.
 *
 * For example given the string "hello %(myName)" and the map <code>
 *      <p>Map<String, Object> map = new HashMap<String, Object>();</p>
 *      <p>map.put("myName", "world");</p>
 * </code>
 *
 * the call {@code format("hello %(myName)", map)} returns "hello world"
 *
 * It replaces every occurrence of a named placeholder with its given value
 * in the map. If there is a named place holder which is not found in the
 * map then the string will retain that placeholder. Likewise, if there is
 * an entry in the map that does not have its respective placeholder, it is
 * ignored.
 *
 * @param str
 *            string to format
 * @param values
 *            to replace
 * @return formatted string
 */
public static String format(String str, Map<String, Object> values) {

    StringBuilder builder = new StringBuilder(str);

    for (Entry<String, Object> entry : values.entrySet()) {

        int start;
        String pattern = "%(" + entry.getKey() + ")";
        String value = entry.getValue().toString();

        // Replace every occurence of %(key) with value
        while ((start = builder.indexOf(pattern)) != -1) {
            builder.replace(start, start + pattern.length(), value);
        }
    }

    return builder.toString();
}

您应该看看官方的ICU4J库。它提供了一个类似于JDK的MessageFormat类,但前者支持命名占位符。

与本页提供的其他解决方案不同。ICU4j是ICU项目的一部分,由IBM维护并定期更新。此外,它还支持高级用例,如多元化等。

下面是一个代码示例:

MessageFormat messageFormat =
        new MessageFormat("Publication written by {author}.");

Map<String, String> args = Map.of("author", "John Doe");

System.out.println(messageFormat.format(args));