StrUtil

StrUtil currently provides simple template replacement and array/list joining. It does not provide padding, character counting, or membership helpers.

Templates

The Map overload replaces ${name} placeholders. Missing or null map values become empty strings.

Map<String, Object> values = new HashMap<>();
values.put("name", "Ada");
String message = StrUtil.simpleTpl("Hello, ${name}! ${missing}", values);
// Hello, Ada!

The JavaBean overload replaces #{property} placeholders with readable bean properties. A null bean property becomes the text null; write-only properties are skipped. Replacement values are literal, so $ and backslashes are safe. If a getter fails, the thrown RuntimeException identifies the property and retains the getter exception as its cause.

String message = StrUtil.simpleTpl("Hello, #{name}!", user);

Join arrays and lists

String array = StrUtil.join(new String[]{"a", null, "c"}, "&");
String list = StrUtil.join(Arrays.asList("a", "b", "c"), "[%s]", ", ");
// a&&c
// [a], [b], [c]

Available overloads accept a generic array, a string array with a format template, and string lists with an optional template. Null elements are rendered as empty strings.

Placeholder and formatting rules

The two template forms deliberately use different placeholder syntax:

Map placeholders match word characters only (${name_1} is valid; ${user.name} is not a placeholder for this API). Unrecognized text remains unchanged. The Bean overload inspects JavaBean getter properties, including inherited ones; it does not read fields directly.

Map<String, Object> values = new HashMap<>();
values.put("path", "$1\\temp");
String result = StrUtil.simpleTpl("path=${path}", values);
// path=$1\temp

This works because replacements are quoted before applying Matcher.appendReplacement; $1 is data, not a regex back-reference. For list joins, the template is passed to String.format, so it should contain an appropriate conversion such as %s.

Choosing the right helper

StrUtil intentionally focuses on small formatting operations. For regular-expression replacement use RegExpHelper; for URL/form encoding use UrlCodec; for bytes, character sets, and hexadecimal conversion use StringBytes.

Implementation notes

The Map template overload scans ${word} with one precompiled Pattern and builds the result with Matcher.appendReplacement / appendTail. Quoting replacement text prevents the regex engine from interpreting $ or backslashes in a value. The Bean overload instead uses JavaBeans introspection and ordinary String.replace for each readable property, which explains both its #{property} syntax and its different null behavior.

Join methods use a StringBuilder and append the delimiter only between elements, avoiding a trailing delimiter. They intentionally do not escape values or apply locale-sensitive formatting; perform those transformations before joining when required.