unix ls command in java

Question

Hi I am trying to list folders in unix "ls" command style in java. I have a folder tree like this :

enter image description here

My file structure is as follows :

private class Node{

    public List<Node> children= new ArrayList<Node>();
    public String value;
    public Node(String value){
        this.value = value;
    }

    public void addSubDirectory(Node child){
        children.add(child);
    }

}

Problem : I am not able to recurse more than the children of current folder when there is nothing after the ' * ' in a command

For eg. command

ls A/B/*/*/E/ and ls A/*/*/M/*/E/ works

But command " ls A/ * " only shows

B Y

Code to traverse

public void showCommand(Node root, String command){
        String argument = command.substring(3);
        System.out.println("command is ls "+argument);
        show(root,argument);   
    }
    private void show(Node root, String cmd){

        int N = cmd.length();
        if(N==0){
            // case when end of command is reached
            for(Node child:root.children){
                System.out.println(child.value);
            }
        }else{
            char c = cmd.charAt(0);
            // case when folder name is present in command
            if((c!='*') && (c!='/')){
                for(Node child:root.children){
                    if(child.value.equals(String.valueOf(c))){
                        show(child,cmd.substring(1));
                    }
                }
                return;
            }else if(c=='*'){  
            // case when * is present in command
            // i think problem lies here
                if(N==1){
                   System.out.println(root.value);
                   preOrderTraverse(root);
                }else{
                  for(Node child:root.children){
                      show(child,cmd.substring(1));
                  }
                }
                return;
            }else if(c=='/'){
            // case when '/' is present in commmand
                show(root,cmd.substring(1));
                return;
            }

        }
    }

you know, the File class provides a lot of methods that can retrieve all the files and directories in a folder... — Mark W
– Mark W, Commented Jul 5, 2014 at 15:45
Hi Mark, just trying to model files as a tree and use file traversal to visit all files — sreeprasad
– sreeprasad, Commented Jul 5, 2014 at 15:52

user3679868 · Accepted Answer · 2014-07-05 16:00:57Z

1

When the last char in the command is a *, you call back the showCommand method with an empty cmd and when the method receives an empty cmd string the recursion stops.

When the current char c is a *, you should check it's the last char in cmd, if it is then you should send the current cmd instead of cmd.substring(1). That way it should go through the hierarchy recursively.

answered Jul 5, 2014 at 16:00

user3679868

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1 Comment

sreeprasad Over a year ago

Your idea worked with a small change. I wrote simple preOrder traversal when '*' is the last character of the command and called show method other wise. I have edited and updated the corrected code

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