1到9之间插入加减符号，使算式等于100

import java.util.*;
import javax.script.*;

public class HelloWorld {
    static ScriptEngine jse = new ScriptEngineManager().getEngineByName("JavaScript");  
    public static void combine(List<String> list,String s, int n)
    {
        if(n==8){
            list.add(s+"+"+9);
            list.add(s+"-"+9);
            list.add(s+"@"+9);
        }else{
            int a = n+1;
            String s1 = s+"+"+a;
            combine(list,s1,n+1);
            String s2 = s+"-"+a;
            combine(list,s2,n+1);
            String s3 = s+"@"+a;
            combine(list,s3,n+1);
        }
        
    }

    public static void main(String[] args) throws Exception {
        List<String> list  = new ArrayList<String>();
        combine(list,"1",1);
        //System.out.println(list.size());
        for(String str:list){
            str = str.replaceAll("@","");
            Double res = (Double)jse.eval(str);
            if(res==100){
                System.out.println(str+"=100");
            }
        }
    }

}