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)?
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
public static String format(String format, Map<String, Object> values) {
StringBuilder formatter = new StringBuilder(format);
List<Object> valueList = new ArrayList<Object>();
Matcher matcher = Pattern.compile("\\$\\{(\\w+)}").matcher(format);
while (matcher.find()) {
String key = matcher.group(1);
String formatKey = String.format("${%s}", key);
int index = formatter.indexOf(formatKey);
if (index != -1) {
formatter.replace(index, index + formatKey.length(), "%s");
valueList.add(values.get(key));
}
}
return String.format(formatter.toString(), valueList.toArray());
}
例子:
String format = "My name is ${1}. ${0} ${1}.";
Map<String, Object> values = new HashMap<String, Object>();
values.put("0", "James");
values.put("1", "Bond");
System.out.println(format(format, values)); // My name is Bond. James Bond.
其他回答
谢谢你的帮助!使用所有的线索,我写了一个例程来做我想要的——使用字典的类似python的字符串格式化。因为我是Java新手,任何提示都是感激的。
public static String dictFormat(String format, Hashtable<String, Object> values) {
StringBuilder convFormat = new StringBuilder(format);
Enumeration<String> keys = values.keys();
ArrayList valueList = new ArrayList();
int currentPos = 1;
while (keys.hasMoreElements()) {
String key = keys.nextElement(),
formatKey = "%(" + key + ")",
formatPos = "%" + Integer.toString(currentPos) + "$";
int index = -1;
while ((index = convFormat.indexOf(formatKey, index)) != -1) {
convFormat.replace(index, index + formatKey.length(), formatPos);
index += formatPos.length();
}
valueList.add(values.get(key));
++currentPos;
}
return String.format(convFormat.toString(), valueList.toArray());
}
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));
我试了一下
public static void main(String[] args)
{
String rowString = "replace the value ${var1} with ${var2}";
Map<String,String> mappedValues = new HashMap<>();
mappedValues.put("var1", "Value 1");
mappedValues.put("var2", "Value 2");
System.out.println(replaceOccurence(rowString, mappedValues));
}
private static String replaceOccurence(String baseStr ,Map<String,String> mappedValues)
{
for(String key :mappedValues.keySet())
{
baseStr = baseStr.replace("${"+key+"}", mappedValues.get(key));
}
return baseStr;
}
jakarta commons lang的StrSubstitutor是一种轻量级的实现方法,前提是您的值已经被正确格式化。
http://commons.apache.org/proper/commons-lang/javadocs/api-3.1/org/apache/commons/lang3/text/StrSubstitutor.html
Map<String, String> values = new HashMap<String, String>();
values.put("value", x);
values.put("column", y);
StrSubstitutor sub = new StrSubstitutor(values, "%(", ")");
String result = sub.replace("There's an incorrect value '%(value)' in column # %(column)");
上述结果为:
“第2列中的“1”值不正确”
当使用Maven时,您可以将此依赖项添加到pom.xml:
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
<version>3.4</version>
</dependency>
基于这个答案,我创建了MapBuilder类:
public class MapBuilder {
public static Map<String, Object> build(Object... data) {
Map<String, Object> result = new LinkedHashMap<>();
if (data.length % 2 != 0) {
throw new IllegalArgumentException("Odd number of arguments");
}
String key = null;
Integer step = -1;
for (Object value : data) {
step++;
switch (step % 2) {
case 0:
if (value == null) {
throw new IllegalArgumentException("Null key value");
}
key = (String) value;
continue;
case 1:
result.put(key, value);
break;
}
}
return result;
}
}
然后我创建类StringFormat用于字符串格式化:
public final class StringFormat {
public static String format(String format, Object... args) {
Map<String, Object> values = MapBuilder.build(args);
for (Map.Entry<String, Object> entry : values.entrySet()) {
String key = entry.getKey();
Object value = entry.getValue();
format = format.replace("$" + key, value.toString());
}
return format;
}
}
你可以这样用:
String bookingDate = StringFormat.format("From $startDate to $endDate"),
"$startDate", formattedStartDate,
"$endDate", formattedEndDate
);