替换字符串中符合正则表达式规则的子串

import java.util.regex.*;

public class RegReplace{

    public static void main(String[] args){
        
        Pattern p = Pattern.compile("java",Pattern.CASE_INSENSITIVE);
        Matcher m = p.matcher("jaVa JAva I love JAVa fwafasfvasv");
        System.out.println(m.replaceAll("java"));
        
        StringBuffer sb = new StringBuffer();
        int i = 0;
        m.reset();
        while(m.find()){
            i++;
            if(i%2 == 0){
                m.appendReplacement(sb,"JAVA");
            } else {
                m.appendReplacement(sb,"java");
            }
      }
        System.out.println(m.appendTail(sb));
    }

}