public class Main { public static void main(String[] args) {

 String[] fields = { "name", "position", "salary" }; 

 String table = "employee";

 String insert = buildInsertSql(table, fields);

 System.out.println(insert);

 String s = "INSERT INTO employee (name, position, salary) VALUES (?, ?, ?)"; System.out.println(s.equals(insert) ? "测试成功" : "测试失败"); }

    static String buildInsertSql(String table, String[] fields) {

        // TODO:

        return "INSERT INTO employee ("+fields[0]+", "+fields[1]+", "+fields[2]+") VALUES (?, ?, ?)";

    }

stringbuilder之所以可以不改变字符数组对象就能改变字符串是因为它有append方法，append方法又是通过getChars方法实现的。看源码不难理解。