適当JSON

gistfile1.java

import java.nio.CharBuffer;
import java.util.HashMap;
import java.util.Map;

public class Parser {
    
    public static final char START_OBJECT = '{';
    public static final char KEY = ':';
    public static final char VALUE = ',';
    public static final char END_OBJECT = '}';

    private CharBuffer buffer;
    private char current;

    public Parser(CharBuffer buffer) {
        this.buffer = buffer;
    }
    
    public Parser(String json) {
        this.buffer = CharBuffer.wrap(json);
    }

    private Object pull() {
        StringBuilder sb = new StringBuilder();
        while (true) {
            current = buffer.get();
            if (current == START_OBJECT || current == KEY || current == VALUE || current == END_OBJECT) {
                break;
            }
            sb.append(current);
        }
        String s = sb.toString();
        if (s.isEmpty()) {
            return null;
        }
        if (s.charAt(0) == '"' && s.charAt(s.length() - 1) == '"') {
            return s.substring(1, s.length() - 1);
        } else {
            return Integer.parseInt(s);
        }
    }
    
    public Object parse() {
        HashMap map = new HashMap();
        String key = "";
        PARSE:
        do {
            Object val = pull();
            switch (current) {
            case KEY:
                key = val.toString();
                break;
            case START_OBJECT:
                val = parse();
            case END_OBJECT:
            case VALUE:
                map.put(key, val);
                if (current == END_OBJECT) {
                    break PARSE;
                }
                break;
            }
        } while (buffer.remaining() > 0);
        return map;
    }

    public static void main(String[] args) {
        Parser parser = new Parser("{\"apple\":123,\"orange\":456,\"hoge\":{\"xyz\":\"test\"}}");
        Map map = (Map) parser.parse();
        System.out.print(map);
    }

}