Multi thread but resource is conflict.

ThreadMulti.java

import java.util.stream.Stream;

public class ThreadMulti {
    static class Context{
        String str;
        int i = 0;
        boolean inParenthesis = false;
        boolean terminated = false;
        Context(String str){
            this.str = str;
        }
    }
    
    public static void main(String[] args) {
        StringBuilder sb = new StringBuilder();
        
        Context[] ctxs = {
            new Context("abc(def)gh(ijk)lmn"),
            new Context("(abc)def(gh)ijk(lmn)")};
        int ctxId = 0;
        
        while(Stream.of(ctxs).anyMatch(c -> !c.terminated)){
            Context ctx = ctxs[ctxId];
            ctxId = (ctxId + 1) % ctxs.length;
            if(ctx.terminated){
                continue;
            }
            if(ctx.i >= ctx.str.length()){
                ctx.terminated = true;
                continue;
            }
            char ch = ctx.str.charAt(ctx.i);
            switch(ch){
                case '(':
                    ctx.inParenthesis = true;
                    break;
                case ')':
                    ctx.inParenthesis = false;
                    break;
                default:
                    if(ctx.inParenthesis){
                        sb.append(ch);
                    }
            }
            ++ctx.i;
        }
        System.out.println(sb);
    }
}