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 common string operations including validation, concatenation, padding, templating, and encoding conversions.

Main Features

• String validation and empty checks
• URL path concatenation
• String templating with placeholders
• String padding and formatting
• List/array joining with custom delimiters
• UTF-8 encoding/decoding utilities
• Pattern matching and replacement

Constants

1. EMPTY_STRING - Empty string constant
2. DELIM_STR - Default template delimiter "{}"

Methods

1. Validation

1. hasText(String str) - Check if string contains actual text
2. isEmptyText(String str) - Opposite of hasText()

2. Concatenation

1. concatUrl(String a, String b) - Smart URL path concatenation
2. join(T[] arr, String str) - Join array with delimiter
3. join(List<T> list, String str) - Join list with delimiter
4. join(List<String> list, String tpl, String str) - Join with template formatting

3. Templating

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

4. Utilities

1. charCount(String str, String _char) - Count character occurrences
2. leftPad(String str, int len, String _char) - Left pad string
3. isWordOneOfThem(String word, String[] arr) - Check string in array
4. getUTF8_Bytes(String str) - Get UTF-8 bytes
5. byte2String(byte[] bytes) - Convert bytes to UTF-8 string
6. byte2String(String str) - Re-encode string as UTF-8

Usage Examples

Validation

boolean valid = StrUtil.hasText("  test  "); // true
boolean empty = StrUtil.isEmptyText("   "); // true

URL Concatenation

String url = StrUtil.concatUrl("http://example.com", "api"); 
// "http://example.com/api"

Templating

String result = StrUtil.print("Hello {}!", "World"); // "Hello World!"
String tpl = StrUtil.simpleTpl("Name: ${name}", Map.of("name", "John")); 
// "Name: John"

Joining

String joined = StrUtil.join(List.of("a","b","c"), ","); // "a,b,c"

Encoding

byte[] bytes = StrUtil.getUTF8_Bytes("test");
String str = StrUtil.byte2String(bytes); // "test"

Conclusion

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