java获取文件路径的不同方式与不同结果

package cn.loubth.web;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.io.IOException;

@WebServlet(name = "ServletTest")
public class ServletTest extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

//-------------------------------第一类--------------------------------------------------------
        String path1=this.getClass().getResource("").getPath();
        //结果：   /C:/Users/Administrator/IdeaProjects/FirstWebProject/out/artifacts/FirstWebProject_war_exploded/WEB-INF/classes/cn/loubth/web/
        //String path2=this.getClass().getResource(".").getPath();
        //结果：   报错，空指针异常
        String path3=this.getClass().getResource("/").getPath();
        //结果：   /C:/Users/Administrator/IdeaProjects/FirstWebProject/out/artifacts/FirstWebProject_war_exploded/WEB-INF/classes/
        String path4=this.getClass().getResource("\\").getPath();
        //结果：   /C:/Users/Administrator/IdeaProjects/FirstWebProject/out/artifacts/FirstWebProject_war_exploded/WEB-INF/classes/cn/loubth/web/

//-------------------------------第二类--------------------------------------------------------

        String path5=this.getClass().getClassLoader().getResource("").getPath();
        //结果：   /C:/Users/Administrator/IdeaProjects/FirstWebProject/out/artifacts/FirstWebProject_war_exploded/WEB-INF/classes/
        String path6=this.getClass().getClassLoader().getResource(".").getPath();
        //结果：   /C:/apache-tomcat-7.0.77-windows-x64/apache-tomcat-7.0.77/lib/
        String path7=this.getClass().getClassLoader().getResource("/").getPath();
        //结果：   /C:/Users/Administrator/IdeaProjects/FirstWebProject/out/artifacts/FirstWebProject_war_exploded/WEB-INF/classes/
        String path8=this.getClass().getClassLoader().getResource("\\").getPath();
        //结果：   /C:/Users/Administrator/IdeaProjects/FirstWebProject/out/artifacts/FirstWebProject_war_exploded/WEB-INF/classes/

//-------------------------------第三类--------------------------------------------------------

        String path9=new File("").getAbsolutePath();
        //结果：   C:\apache-tomcat-7.0.77-windows-x64\apache-tomcat-7.0.77\bin
        String path10=new File(".").getAbsolutePath();
        //结果：   C:\apache-tomcat-7.0.77-windows-x64\apache-tomcat-7.0.77\bin\.
        String path11=new File("/").getAbsolutePath();
        //结果：   C:\
        String path12=new File("\\").getAbsolutePath();
        //结果：   C:\

//-------------------------------输出结果--------------------------------------------------------
        
        System.out.println(path1);
        //System.out.println(path2);    //因为报错所以就不输出了
        System.out.println(path3);
        System.out.println(path4);
        System.out.println(path5);
        System.out.println(path6);
        System.out.println(path7);
        System.out.println(path8);
        System.out.println(path9);
        System.out.println(path10);
        System.out.println(path11);
        System.out.println(path12);

    }
}