CODEWITHSUNDEEP
javaspring
Prathap
Prathap

Reputation: 1033

Replace string placeholder value in java (conditions apply)

My question might be little odd. I have below condition in String

String condition="((1 || 3) && 4)"; ***//I am fine to add special characters in this condition as well..***

In my code, I need to dynamically evaluate expression by replacing number values with ArrayList.get as below:

boolean result=(someArrayList.get(1).isResult() || someArrayList.get(3).isResult()) && someArrayList.get(4).isResult();

My question is that, how can I easily replace numbers (1,3,4) in above condition with someArrayList.get(1)... I can write logic to do it, but trying to see if there's any easy API to use it.

Upvotes: 0

Views: 354

Answers (2)

Andy Turner
Andy Turner

Reputation: 140514

Just use replaceAll:

String condition="((1 || 3) && 4)";
String newCondition = condition.replaceAll("(\\d+)", "someArrayList.get($1).isResult()");

Ideone Demo

((someArrayList.get(1).isResult() || someArrayList.get(3).isResult()) && someArrayList.get(4).isResult())

Upvotes: 1

Arvind Kumar Avinash
Arvind Kumar Avinash

Reputation: 79550

You can do it as follows:

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Main {
    public static void main(String[] args) {
        String condition = "((1 || 3) && 4)";
        StringBuilder sb = new StringBuilder(condition);
        Pattern p = Pattern.compile("\\d+");
        Matcher m = p.matcher(condition);
        int index, fromIndex = 0, upTo;
        while (m.find()) {
            String num = m.group();
            index = sb.indexOf(num, fromIndex);
            upTo = index + num.length();
            sb.replace(index, upTo, "someArrayList.get(" + num + ").isResult()");
            fromIndex = upTo;
        }
        System.out.println(sb);
    }
}

Output:

((someArrayList.get(1).isResult() || someArrayList.get(3).isResult()) && someArrayList.get(4).isResult())

Upvotes: 1

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