I am working on a format parser in Java and have some trouble with that. The format is stored so that users can change it to their likings.
format: '[prefix] [name] [suffix]: [msg]'
To put my values in the format I use String.replace() in Java.
format = getFormatTemplate(); // '[prefix] [name] [suffix]: [msg]'
format = format.replace("[prefix]", prefix); // prefix = "Hello";
format = format.replace("[name]", name); // name = "username";
format = format.replace("[suffix]", suffix); // suffix = "World";
format = format.replace("[msg]", msg); // msg = "Test message";
This will result in the output Hello username World: Test message as I expect. But when some parts of the string are empty there will be a space there.
When for example the suffix is empty the output will be Hello username : Test message note the space between the name and the :
How can I get rid of that so that some parts can be empty without breaking the user defined format?
Is there a better way to parse and apply the format?
The following method will do the job:
static String replace(String text, Map<String, String> values) {
StringBuilder result = new StringBuilder();
int textIdx = 0;
for (int startIdx; (startIdx = text.indexOf('[', textIdx)) != -1; ) {
int endIdx = text.indexOf(']', startIdx + 1);
if (endIdx == -1)
break;
result.append(text.substring(textIdx, startIdx));
textIdx = endIdx + 1;
String value = values.get(text.substring(startIdx + 1, endIdx));
if (value != null && ! value.isEmpty()) {
result.append(value); // Replace placeholder with non-empty value
} else if (result.length() != 0 && result.charAt(result.length() - 1) == ' ') {
result.setLength(result.length() - 1); // Remove space before placeholder
} else if (textIdx < text.length() && text.charAt(textIdx) == ' ') {
textIdx++; // Skip space after placeholder
}
}
result.append(text.substring(textIdx));
return result.toString();
}
Test
public static void main(String[] args) {
test("[prefix] [name] [suffix]: [msg]",
Map.of("prefix", "Hello",
"name", "username",
"suffix", "World",
"msg", "Test message"));
test("[prefix] [name] [suffix]: [msg]",
Map.of("name", "username",
"suffix", "World",
"msg", "Test message"));
test("[prefix] [name] [suffix]: [msg]",
Map.of("prefix", "Hello",
"suffix", "World",
"msg", "Test message"));
test("[prefix] [name] [suffix]: [msg]",
Map.of("prefix", "Hello",
"name", "username",
"msg", "Test message"));
test("[prefix] [name] [suffix]: [msg]",
Map.of("prefix", "Hello",
"name", "username",
"suffix", "World"));
test("[prefix] [name] [suffix]: [msg]",
Map.of());
}
static void test(String text, Map<String, String> values) {
System.out.println('"' + replace(text, values) + '"');
}
Output
"Hello username World: Test message"
"username World: Test message"
"Hello World: Test message"
"Hello username: Test message"
"Hello username World:"
":"
Notice how multiple spaces are correctly eliminated when consecutive placeholders are missing/empty.
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