1 自定义代码实现

1.1 驼峰转下划线

// 自定义正则表达式
private static final Pattern HUMP_PATTERN = Pattern.compile("[A-Z0-9]");

private String humpToLine(String str) {
    Matcher matcher = HUMP_PATTERN.matcher(str);
    StringBuffer sb = new StringBuffer();
    while (matcher.find()) {
        matcher.appendReplacement(sb, "_" + matcher.group(0).toLowerCase());
    }
    matcher.appendTail(sb);
    return sb.toString();
}

1.2 下划线转驼峰

private static final char UNDERLINE = '_';

private String underlineToCamel(String param) {
    if (StringUtils.isBlank(param)) {
        return "";
    }
    int len = param.length();
    StringBuilder sb = new StringBuilder(len);
    for (int i = 0; i < len; i++) {
        char c = Character.toLowerCase(param.charAt(i));
        if (c == UNDERLINE) {
            if (++i < len) {
                sb.append(Character.toUpperCase(param.charAt(i)));
            }
        } else {
            sb.append(c);
        }
    }
    return sb.toString();
}

2 使用 Guava 实现

使用 Guava 的话需要 Maven 项目引入依赖

<dependency>
    <groupId>com.google.guava</groupId>
    <artifactId>guava</artifactId>
    <version>21.0</version>
</dependency>

2.1 驼峰转下划线

import com.google.common.base.CaseFormat;
import lombok.extern.slf4j.Slf4j;
import org.junit.Test;

@Slf4j
public class ConvertLineToHumpTest {

    @Test
    public void convertLineToHumpTest() {
        String resultStr = CaseFormat.LOWER_CAMEL.to(CaseFormat.LOWER_UNDERSCORE, "studentName");
        log.info("  >>> 驼峰转下划线 : {}", resultStr);
    }
}
   >>> 驼峰转下划线 : student_name

2.2 下划线转驼峰

import com.google.common.base.CaseFormat;
import lombok.extern.slf4j.Slf4j;
import org.junit.Test;

@Slf4j
public class ConvertHumpToLineTest {

    @Test
    public void convertHumpToLineTest() {
        String resultStr = CaseFormat.LOWER_UNDERSCORE.to(CaseFormat.LOWER_CAMEL, "student_name");
        log.info("  >>> 下划线转驼峰 : {}", resultStr);
    }
}
   >>> 下划线转驼峰 : studentName

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