Matching a SubString in java

Question

I have an input data stored in an arraylist. while iterating through the list the output is

Input ----------- [0 Overcast 1 High 2 Normal 3 Weak ]
Input ----------- [0 Rainy 1 Mild 2 High 3 Strong ]
Input ----------- [0 Rainy 1 Mild 2 Normal 3 Weak ]

and rule in another arraylist

Rule -----------[ 0 Overcast Yes, 0 Rainy 3 Strong No, 0 Rainy 3 Weak Yes, 0 Sunny 2 High No, 0 Sunny 2 Normal Yes]

I am expecting the output as

[0 Overcast 1 High 2 Normal 3 Weak Yes]
[0 Rainy 1 Mild 2 High 3 Strong No]
[0 Rainy 1 Mild 2 Normal 3 Weak Yes]

By looking into rule set I have to add label to input. For that I tried to match between input and rule set

for(String ruleSet : addRule){ //ruleset
 for(String lineSet : getLine){ //inputline
   if (lineSet.matches("(.*)"+ruleSet+"(.*)")) {
     System.out.println("got----------------"+lineSet+"***"+ruleSet);
     break;
   }
   else{
     System.out.println("Not found----------------"+lineSet+"***"+ruleSet);
   }
 }
}

But my result is like this

0 Overcast 1 High 2 Normal 3 Weak Yes is not matching with 0 Overcast Yes. Eventhough it is a subset.

Am I doing anything wrong.

Answer 1

If I understand correctly, you have two lists of String:

1. getLine is a list of strings representing lines of input
2. addRule is a list of strings representing rule sets.

Each rule contains several parts that need to match against the input line, and a result that should be used in case of a match.

(You seem to call this result "classpath", though that term has a very specific meaning in the context of Java).

So the line:

0 Overcast 1 High 2 Normal 3 Weak

Would match against the rule

0 Overcast

because it contains the substring "0 Overcast", but also against the rule:

0 Overcast 3 Weak

because the line contains the substrings "0 Overcast" and "3 Weak", even though the entire rule does not appear as a substring in the line.

I guess what you were looking for is a subset search, and maybe saw this answer and tried to use it, but doing a subset match between strings is complicated, and using a regular expression is possible, but a little trickier than what you tried, so I'd recommend trying to go with a simpler solution.

Specifically, just doing .matches("(.*)"+ruleSet+"(.*)") will not do what you want.

If I'm correct in my interpretation of your problem, let me know in the comments, and I'll try to help you find a solution.

Continued

So, assuming you have control of the rule set, I would probably make a Rule class that looks something like this:

public class Rule {
    public List<String> parts;
    public String result;

    public Rule(String result, String... parts) {
        this.parts = new ArrayList<>();
        for(String part : parts) {
            this.parts.add(part);
        }
        this.result = result;
    }

    public String match(String line) {
        for(String part : parts) {
            if (!line.contains(part)) return null;
        }
        return result;
    }
}

Notice how match is implemented: if any of the parts don't match, then the match fails.

(I used varargs for the constructor, but you can just pass a list if you want).

Then you can initialize the rule set like this:

List<Rule> ruleSet = new ArrayList<>();
ruleSet.add(new Rule("Yes", "0 Overcast"));
ruleSet.add(new Rule("No", "0 Rainy", "3 Strong"));
ruleSet.add(new Rule("Yes", "0 Rainy", "3 Weak"));
...

And when you loop against the rules, call match to get null if there's no match, or the result if there is a match.

for(Rule rule : ruleSet) {
    for(String line : getLine) {
       String result = rule.match(line);
       if (result != null) {
          ...

---

Alternatively, you can write the rules as regular expressions like this:

String rule = ".*0 Rainy.*3 Strong.*";
if(line.matches(rule)) {
    ...

But you should probably avoid regular expressions until you've had some time to learn about them. They're powerful tools, but have many caveats.

---

If you need to keep the rule set in a text file, then you're going to have to write a method to convert the lines into a Rule object, possibly as a different constructor. Here's one way to do it:

public class Rule {
    ...
    public Rule(String line) {
        this.parts = new ArrayList<>();
        String number = null;
        for (String s : line.split()) {
            if (s.equals("Yes") || s.equals("No")) {
                this.result = s;
                return;
            }
            if (number == null) {
                number = s;
            } else {
                this.parts.add(number + " " + s);
                number = null;
            }
        }
    }