java：驼峰转下划线
package com.xiaoxu.crawler.utils;
import com.google.common.collect.Lists;
import com.xiaoxu.crawler.excp.CrawlerForJException;
import org.apache.commons.lang3.ArrayUtils;
import org.springframework.util.CollectionUtils;
import org.springframework.util.StringUtils;
import java.text.MessageFormat;
import java.util.List;
/**
* @author xiaoxu
* @date 2022-11-19 21:52
* crawlerJ:
*/
public class StrUtils {
private static final String underLineMark = "_";
private static final String EMPTY_STRING = "";
public static boolean equals(String a, String b){
if(null == a){
return null == b;
}
return a.equals(b);
}
public static int getMatchCount(String str, String subStr){
if(!StringUtils.hasLength(str) || !StringUtils.hasLength(subStr)){
ExcpUtils.throwExp(
MessageFormat.format("getMatchCount's str and subStr should not be null or empty:{0},{1}.",
str, subStr));
}
return StringUtils.countOccurrencesOf(str, subStr);
}
/**
* @param name 小驼峰命名Str
* @return 下划线
*/
@SuppressWarnings("all")
public static String humpTransferUnderline(String name){
// null or empty throw exp
ExcpUtils.throwExpIfFalse(StringUtils.hasLength(name), "when hump transfer to underline, name should not be empty.");
CharSequence cs = name;
List<CharSequence> charSequenceList = Lists.newArrayList();
int temI = 0, i = 0, csLen = 0;
for (; i < (csLen = cs.length()); i++) {
char c = cs.charAt(i);
if(Character.isUpperCase(c)){
CharSequence csq = cs.subSequence(temI, i);
if(csq.length() > 0){
addCharSequence(charSequenceList, csq);
temI = i;
}
}
}
CharSequence lastSequence = cs.subSequence(temI, csLen);
if(lastSequence.length() > 0){
addCharSequence(charSequenceList, lastSequence);
}
// actual could not execute this
if(CollectionUtils.isEmpty(charSequenceList)) return EMPTY_STRING;
return String.join(underLineMark, charSequenceList);
}
private static void addCharSequence(List<CharSequence> charSequenceList, CharSequence charSequence) {
if(null == charSequenceList){
throw new CrawlerForJException("charSequenceList could not be null");
}
if(null == charSequence || charSequence.length() <= 0){
throw new CrawlerForJException("charSequence need non empty");
}
char[] csqChars = charSequence.toString().toCharArray();
char[] initialLowerCsqChar = new char[csqChars.length];
initialLowerTransfer(initialLowerCsqChar, csqChars);
charSequenceList.add(new String(initialLowerCsqChar));
}
private static void initialLowerTransfer(char[] targetChar, char[] originChar){
ExcpUtils.throwExpIfFalse(ArrayUtils.isNotEmpty(targetChar), "targetChar is empty");
ExcpUtils.throwExpIfFalse(ArrayUtils.isNotEmpty(originChar), "originChar is empty");
int totalLength;
ExcpUtils.throwExpIfFalse((totalLength = originChar.length) == targetChar.length, "targetChar'length not equals to originChar's length");
char[] temp;int tempSize;
System.arraycopy((temp = new char[]{Character.toLowerCase(originChar[0])}), 0 , targetChar, 0, (tempSize = temp.length));
if(totalLength > tempSize){
System.arraycopy(originChar, tempSize, targetChar, tempSize, totalLength - tempSize);
}
}
public static void main(String[] args) {
System.out.println(humpTransferUnderline("a"));
System.out.println(humpTransferUnderline("A"));
System.out.println(humpTransferUnderline("age"));
System.out.println(humpTransferUnderline("Age"));
System.out.println(humpTransferUnderline("ageABBadA"));
System.out.println(humpTransferUnderline("AddressFrom"));
System.out.println(humpTransferUnderline("gmt_create"));
System.out.println(humpTransferUnderline("gmtCreate"));
}
}