StrUtil Tutorial

This tutorial provides an overview of the StrUtil class, which is part of the lightweight-component/aj-util library. The StrUtil class provides utility methods for string manipulation in Java applications.

Introduction

The StrUtil class contains static methods for counting, padding, templating, joining, and membership checks.

Main Features

• String templating with placeholders
• String padding and formatting
• List/array joining with custom delimiters

Methods

1. Joining

1. join(T[] arr, String str) - Join an array with a delimiter
2. join(List<String> list, String str) - Join a string list with a delimiter
3. join(List<String> list, String tpl, String str) - Format and join a string list

Array and list overloads serialize a null element as an empty string.

3. Templating

1. simpleTpl(String template, Map<String, Object> params) - ${var} replacement
2. simpleTpl2(String template, Map<String, Object> data) - #{var} replacement
3. simpleTpl(String template, Object data) - JavaBean property replacement

Replacement values are treated literally, so $ and \ are safe in values. JavaBean templating skips write-only properties. If a getter fails, the thrown RuntimeException identifies the property and retains the getter failure as its cause.

4. Utilities

1. charCount(String str, String _char) - Count occurrences, including overlapping matches
2. leftPad(String str, int len, String padding) - Pad to exactly len characters without changing whitespace already in str
3. isWordOneOfThem(String word, String[] arr) - Check string in array

Usage Examples

Templating

Map<String, Object> values = new HashMap<>();
values.put("name", "John");
String tpl = StrUtil.simpleTpl("Name: ${name}", values);
// "Name: John"

Counting and padding

int count = StrUtil.charCount("aaa", "aa"); // 2: overlapping matches are counted
String padded = StrUtil.leftPad("a b", 6, "$"); // "$$$a b"

Joining

String joined = StrUtil.join(Arrays.asList("a", "b", "c"), ","); // "a,b,c"

Conclusion

The StrUtil class provides comprehensive utility methods for string manipulation, making common string operations more convenient in Java applications.