使用StringBuilder,StringJoiner构造一个INSERT语句

请使用StringBuilder构造一个INSERT语句：

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:使用StringBuilder拼接字符串
        StringBuilder s=new StringBuilder();
        s.append("INSERT INTO ");
        s.append(table);
        s.append(" (");
        for (int i = 0; i < fields.length; i++) {
            if (i < fields.length - 1) {
                s.append( fields[i] + ", " );
            } else {
                s.append( fields[i] );
            }
        }
        s.append(") VALUES (?, ?, ?)");
        return s.toString();
    }
}

还可以使用StringJoiner,可以发现使用StringJoiner后代码简化了很多
语法：StringJoiner s=new StringJoiner(间隔符,指定开头字符串（可省）,指定结尾字符串（可省）)

import java.util.StringJoiner;
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:使用StringJoiner拼接字符串
        StringJoiner sj = new StringJoiner(", ","INSERT INTO "+table+" (",") VALUES (?, ?, ?)");
        for (String field : fields) {
            sj.add(field);
        }
        return sj.toString();
    }
}

String.join()：String还提供了一个静态方法join()，这个方法在内部使用了StringJoiner来拼接字符串，在不需要指定“开头”和“结尾”的时候，用String.join()更方便：

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:使用String.join和StringBuilder拼接字符串
        String s = String.join(", ", fields);
        StringBuilder sd = new StringBuilder();
        sd.append("INSERT INTO "+table+" (");
        sd.append(s);
        sd.append(") VALUES (?, ?, ?)");
        return sd.toString();
    }
}