java.io.FileNotFoundException：text.txt（系统找不到指定的文件）

我的以下代码有问题。完整的错误如下所示：

java.io.FileNotFoundException: text.txt (The system cannot find the file specified)
at java.io.FileInputStream.open0(Native Method)
at java.io.FileInputStream.open(Unknown Source)
at java.io.FileInputStream.<init>(Unknown Source)
at java.util.Scanner.<init>(Unknown Source)
at AAlg.main.main(main.java:42)

这是代码：

package AAlg;

import java.io.File;
import java.io.FileNotFoundException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Scanner;

public class main {

    public static void main(String[] args) {

        try {


            Scanner s = new Scanner(new File("words.txt"));

            ArrayList<String> a =new ArrayList<String>();

            while(s.hasNextLine()) {
                a.add(s.nextLine());
            }


            Collections.sort(a);

            ArrayList<Node> nodes = new ArrayList<Node>();

            for(int i=0;i<a.size();i++) {
                nodes.add(new Node(a.get(i)));
            }

        //  System.out.println(a.toString());



            BBST b = new BBST();

            b.root = b.add(nodes, 0, nodes.size()-1);

            long start_time = System.nanoTime();    
            Scanner s2 = new Scanner(new File("text.txt"));


            while(s2.hasNext()) {
                String ss = s2.next();
            //  System.out.println(ss);
                b.find(ss.toLowerCase());
            }


            long end_time = System.nanoTime();
            System.out.print((end_time - start_time) / 1e6);





        //  s2.preorder(s2.root);

        //  System.out.print(nodes.get(nodes.size()/2).left.value);

        //  s2.add(a, 0, a.size()-1);

        //  System.out.println(a.size());




        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }


    }

}

class BBST{

    Node root;

    public BBST() {
        root=null;
    }




    public Node add(ArrayList<Node> nodes,int start,int end) {


        if(start > end)
            return null;

        int mid = (start+end)/2;

    //  System.out.println();

    //  System.out.println("mid= "+mid+" start= "+start+" end= "+end);

        Node node = nodes.get(mid);



        node.left = add(nodes,start,mid-1);
        node.right = add(nodes,mid+1,end);


        return node;



    }


    boolean find(String value) {


        Node tmp = root;
        Node pre = null;



        while(tmp != null) {



            pre=tmp;

            boolean large = false;

            if(tmp.value.equals(value))
                return true;



            for(int i=0;i<value.length();i++) {


                if(i < tmp.value.length() && i < value.length() && value.charAt(i) != tmp.value.charAt(i)) {
                    if(value.charAt(i) < tmp.value.charAt(i)) {
                        large=true;
                        break;
                    }
                }

            }

            if(large) {
                tmp = tmp.left;
            }
            else {
                tmp = tmp.right;
            }




        }

        return false;
    }

}

class Node  
{ 
    String value; 
    Node left, right; 

    public Node(String value)  
    { 
        this.value=value;
        left=null;
        right=null;
    } 
}