Servlet API中的请求方法常量在哪里？

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class MyServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response) {
        // 处理GET请求
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) {
        // 处理POST请求
    }

    protected void doPut(HttpServletRequest request, HttpServletResponse response) {
        // 处理PUT请求
    }

    protected void doDelete(HttpServletRequest request, HttpServletResponse response) {
        // 处理DELETE请求
    }
}