自己手写的24点程序（包含括号操作，可适应所有四张牌类型，输入用空格隔开，回车结束）

import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Scanner;

import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;

public class Main {
    public static void main(String[] args) throws ScriptException {
        Scanner sc = new Scanner(System.in);
        while(sc.hasNext()) {
            String in = sc.nextLine();
            //in = "j k q a";
            in = in.trim();
            String out = game(in);
            System.out.println(out);
        }
    }

    private static String game(String in) throws ScriptException {
        in = in.toUpperCase();
        String[] ins = in.split("[\\s]+");
        if(ins.length != 4) {return "ERROR";}
        for (int i = 0; i < ins.length; i++) {
            if(ins[i].equals("A")) {ins[i] = "1";}
            if(ins[i].equals("J")) {ins[i] = "11";}
            if(ins[i].equals("Q")) {ins[i] = "12";}
            if(ins[i].equals("K")) {ins[i] = "13";}
            if(ins[i].equals("JOKER")) {return "ERROR";}
        }
        System.out.println(Arrays.asList(ins));
        
        //四张牌排序
        String[] numloc = {"1234","1243","1423","1432","1324","1342",
                "2134","2143","2314","2341","2413","2431",
                "3124","3142","3412","3421","3241","3214",
                "4123","4132","4213","4231","4321","4312"};
        int loc;
        String[] co = {"+","-","*","/"};
        ArrayList<String> list = new ArrayList<>();
        String[][] str = null;
        for (int nl = 0; nl < numloc.length; nl++) {
            str = new String[4][4];        
            for (int j = 0; j < 3; j++) {
                loc = Integer.parseInt(""+numloc[nl].charAt(j))-1;
                for (int j2 = 0; j2 < 4; j2++) {
                    str[j][j2] = ins[loc]+co[j2];
                }
            }
            for (int j = 0; j < 4; j++) {
                loc = Integer.parseInt(""+numloc[nl].charAt(3))-1;
                str[3][j] = ins[loc];
            }
            
            //
            String a = "";
            for (int j1 = 0; j1 < 4; j1++) {
                for (int j2 = 0; j2 < 4; j2++) {
                    for (int j3 = 0; j3 < 4; j3++) {
                        for (int j4 = 0; j4 < 4; j4++) {
                            a=a+str[0][j1]+str[1][j2]+str[2][j3]+str[3][j4];
                            list.add(a);
                            a="";
                        }
                    }
                }
            }
        }
        
        //加括号，共计扩容6倍
        list = new ArrayList<>(new HashSet(list));
        ArrayList<String> list2 = new ArrayList<>();
        for (int i = 0; i < list.size(); i++) {
            String s = list.get(i);
            //记录符号位置
            int[] a = new int[3];
            int count = 0;
            for (int j = 0; j < s.length(); j++) {
                if(s.charAt(j)=='+'||s.charAt(j)=='-'||s.charAt(j)=='*'||s.charAt(j)=='/')
                {a[count++] = j;}
            }
            //System.out.println(s);
            String ss ;
            //第一种
            ss = "("+s.substring(0,a[1])+")"+s.substring(a[1], s.length());
            list2.add(ss);
            //第二种
            ss = "("+s.substring(0,a[2])+")"+s.substring(a[2], s.length());
            list2.add(ss);
            //第三种
            ss = s.substring(0,a[0]+1)+"("+s.substring(a[0]+1, a[2])+")"+s.substring(a[2],s.length());
            list2.add(ss);
            //第四种
            ss = s.substring(0,a[0]+1)+"("+s.substring(a[0]+1, s.length())+")";
            list2.add(ss);
            //第五种
            ss = s.substring(0,a[1]+1)+"("+s.substring(a[1]+1, s.length())+")";
            list2.add(ss);
            //第六种，双括号
            ss = "("+s.substring(0,a[1])+")"+s.substring(a[1],a[1]+1)+"("+s.substring(a[1]+1, s.length())+")";
            list2.add(ss);
            
            //System.out.println(list2);
            //System.out.println("");
            
        }
        list = new ArrayList<>(new HashSet(list));
        list.addAll(list2);
        System.out.println(list);
        //System.out.println(list.size());
        for (int i = 0; i < list.size(); i++) {
            
            Object d = null;
            ScriptEngine se = new ScriptEngineManager().getEngineByName("JavaScript");
            d = (Object) se.eval(list.get(i));
            //System.out.println(i+"  "+d);
            double result = 24D;
            Double re = Double.valueOf(""+d);
            if ( re>(result-0.0001) && re<(result+0.0001) ) {System.out.println("个数:"+list.size()+" "+list2.size());return "结果："+list.get(i); }
            
        }
        System.out.println("个数:"+list.size()+" "+list2.size());
        return "NONE";
    }
}