Latest comments for language 'Java' on doukaku.org

horiuchi's comment on 島の数をカウントする

ついでに島の大きさも数えてますが、今回は関係ないですね。

import java.awt.Point;
import java.util.HashMap;
import java.util.Map;


public class Sample219 {
    private static final char NULL = ' ';

    public Map<Character, Integer> scanIslands(String map) {
        String[] lines = map.split("\n");
        char[][] mapdata = new char[lines.length][];
        for (int index = 0; index < lines.length; index++) {
            mapdata[index] = lines[index].toCharArray();
        }

        Map<Character, Integer> result = new HashMap<Character, Integer>();
        for (Point p = getNextPoint(mapdata); p != null; p = getNextPoint(mapdata)) {
            char c = mapdata[p.y][p.x];
            scan(mapdata, p.x, p.y, c);
            Integer count = result.get(c);
            if (count == null) {
                result.put(c, 1);
            } else {
                result.put(c, count + 1);
            }
        }
        return result;
    }

    private Point getNextPoint(char[][] map) {
        for (int y = 0; y < map.length; y++) {
            for (int x = 0; x < map[y].length; x++) {
                if (map[y][x] != NULL) {
                    return new Point(x, y);
                }
            }
        }
        return null;
    }
    private int scan(char[][] map, int x, int y, char c) {
        if (y < 0 || map.length <= y) return 0;
        if (x < 0 || map[y].length <= x) return 0;
        if (map[y][x] != c) return 0;
        int result = 1;
        map[y][x] = NULL;
        result += scan(map, x + 1, y, c);
        result += scan(map, x, y + 1, c);
        result += scan(map, x - 1, y, c);
        result += scan(map, x, y - 1, c);
        return result;
    }

    public static void main(String[] args) {
        Sample219 sample = new Sample219();
        System.out.println(sample.scanIslands(
                "□■■□\n" +
                "□□■□\n" +
                "□■□□\n" +
                "□■■□"));
        System.out.println(sample.scanIslands(
                "□□□□\n" +
                "■□■□\n" +
                "□■□□\n" +
                "□□□□"));
    }
}

[ Java ] [ download code ] ]

匿名's comment on inline/embeded bytecode assembly

inline/embeded bytecode assembly (Nested Flatten)

固定コードではいまいちなので、ループを完全に展開するようにしました。クラスローダのコンストラクタでコピーする個数を渡します。

import java.lang.reflect.Method;
import java.io.*;

public class Sample extends ClassLoader {
    private static final byte[] PROLOGUE = {-54, -2, -70, -66, 0, 0, 0, 49, 0, 12, 10, 0, 3, 0, 9, 7, 0, 10, 7, 0, 11, 
            1, 0, 6, 60, 105, 110, 105, 116, 62, 1, 0, 3, 40, 41, 86, 1, 0, 4, 67, 111, 100, 101, 1, 0, 4, 99, 111, 
            112, 121, 1, 0, 7, 40, 91, 66, 91, 66, 41, 86, 12, 0, 4, 0, 5, 1, 0, 4, 67, 111, 112, 121, 1, 0, 16, 106, 
            97, 118, 97, 47, 108, 97, 110, 103, 47, 79, 98, 106, 101, 99, 116, 0, 33, 0, 2, 0, 3, 0, 0, 0, 0, 0, 2, 0, 
            1, 0, 4, 0, 5, 0, 1, 0, 6, 0, 0, 0, 17, 0, 1, 0, 1, 0, 0, 0, 5, 42, -73, 0, 1, -79, 0, 0, 0, 0, 0, 9, 0, 
            7, 0, 8, 0, 1, 0, 6};
    private static final byte[] FUNC_DATA = {0, 4, 0, 3};
    private static final byte[] ENTRY = {3,  61};
    private static final byte[] BODY = {42, 28, 43, 28, -124, 2, 1, 51, 84};
    private static final byte[] EPILOGUE = {-79, 0, 0, 0, 0, 0, 0};
    int bytes;

    public Sample(int num) {
        bytes = num;
    }

    @Override
    public Class<?> findClass(String name) throws ClassNotFoundException {
        try {
            ByteArrayOutputStream bs = new ByteArrayOutputStream();
            DataOutputStream os = new DataOutputStream(bs);
            os.write(PROLOGUE);
            os.writeInt(9 * bytes + 15);
            os.write(FUNC_DATA);
            os.writeInt(9 * bytes + 3);
            os.write(ENTRY);
            for (int i = 0; i < bytes; i++)
                os.write(BODY);
            os.write(EPILOGUE);
            byte[] b = bs.toByteArray();
            return defineClass(name, b, 0, b.length);
        } catch (IOException e) {
            throw new ClassNotFoundException(e.getMessage());
        }
    }

    public static void main(String[] args) throws Exception {
        byte[] to = new byte[100];
        byte[] from = new byte[100];
        for (int i = 0; i < from.length; i++)
            from[i] = (byte) i;
        Method[] ms = new Sample(from.length).loadClass("Copy").getMethods();
        ms[0].invoke(null, to, from);
        System.out.println(java.util.Arrays.toString(to));
    }
}

[ Java ] [ download code ] ]

匿名's comment on inline/embeded bytecode assembly

inline/embeded bytecode assembly (Nested Flatten)

クラスローダを作成してバイトコードを直接ソースコード上に記述しました。
ちなみに読み込んだバイトコードは以下のクラスをコンパイルしたものです
（アセンブラで作ったものではありません）。

クラスローダを自作して任意のバイトコードをプログラム中で生成する方法は
「構造リフレクション」をJavaで行う場合の常道のようです。

public class Copy {
	public static void copy(byte[] to, byte[] from) {
		int count = from.length;
		int i = 0;
		switch (count % 8)  /* count > 0 とする */
		 {
		   case 7: to[i] = from[i++];
		   case 6: to[i] = from[i++];
		   case 5: to[i] = from[i++];
		   case 4: to[i] = from[i++];
		   case 3: to[i] = from[i++];
		   case 2: to[i] = from[i++];
		   case 1: to[i] = from[i++];
		   case 0:
		 }
	   	while (i < count) {  
	   		to[i] = from[i++];
	   		to[i] = from[i++];
	   		to[i] = from[i++];
	   		to[i] = from[i++];
	   		to[i] = from[i++];
	   		to[i] = from[i++];
	   		to[i] = from[i++];
	   		to[i] = from[i++];
	   	}
	}
}

import java.lang.reflect.Method;

public class Sample extends ClassLoader {

    @Override
    public Class<?> findClass(String name) throws ClassNotFoundException {
        byte[] b = {
                -54, -2, -70, -66, 0, 0, 0, 49, 0, 24, 7, 0, 2, 1, 0, 4, 67, 111, 112, 121, 7, 0, 4, 1, 0, 16, 106, 
                97, 118, 97, 47, 108, 97, 110, 103, 47, 79, 98, 106, 101, 99, 116, 1, 0, 6, 60, 105, 110, 105, 116, 
                62, 1, 0, 3, 40, 41, 86, 1, 0, 4, 67, 111, 100, 101, 10, 0, 3, 0, 9, 12, 0, 5, 0, 6, 1, 0, 15, 76, 105, 
                110, 101, 78, 117, 109, 98, 101, 114, 84, 97, 98, 108, 101, 1, 0, 18, 76, 111, 99, 97, 108, 86, 97, 
                114, 105, 97, 98, 108, 101, 84, 97, 98, 108, 101, 1, 0, 4, 116, 104, 105, 115, 1, 0, 6, 76, 67, 111, 
                112, 121, 59, 1, 0, 4, 99, 111, 112, 121, 1, 0, 7, 40, 91, 66, 91, 66, 41, 86, 1, 0, 2, 116, 111, 1, 0, 
                2, 91, 66, 1, 0, 4, 102, 114, 111, 109, 1, 0, 5, 99, 111, 117, 110, 116, 1, 0, 1, 73, 1, 0, 1, 105, 1, 
                0, 10, 83, 111, 117, 114, 99, 101, 70, 105, 108, 101, 1, 0, 9, 67, 111, 112, 121, 46, 106, 97, 118, 97, 
                0, 33, 0, 1, 0, 3, 0, 0, 0, 0, 0, 2, 0, 1, 0, 5, 0, 6, 0, 1, 0, 7, 0, 0, 0, 47, 0, 1, 0, 1, 0, 0, 0, 5, 
                42, -73, 0, 8, -79, 0, 0, 0, 2, 0, 10, 0, 0, 0, 6, 0, 1, 0, 0, 0, 1, 0, 11, 0, 0, 0, 12, 0, 1, 0, 0, 0, 
                5, 0, 12, 0, 13, 0, 0, 0, 9, 0, 14, 0, 15, 0, 1, 0, 7, 0, 0, 1, 96, 0, 4, 0, 4, 0, 0, 0, -56, 43, -66, 
                61, 3, 62, 28, 16, 8, 112, -86, 0, 0, 0, 0, 0, 110, 0, 0, 0, 0, 0, 0, 0, 7, 0, 0, 0, 110, 0, 0, 0, 101, 
                0, 0, 0, 92, 0, 0, 0, 83, 0, 0, 0, 74, 0, 0, 0, 65, 0, 0, 0, 56, 0, 0, 0, 47, 42, 29, 43, 29, -124, 3, 
                1, 51, 84, 42, 29, 43, 29, -124, 3, 1, 51, 84, 42, 29, 43, 29, -124, 3, 1, 51, 84, 42, 29, 43, 29, -124,
                3, 1, 51, 84, 42, 29, 43, 29, -124, 3, 1, 51, 84, 42, 29, 43, 29, -124, 3, 1, 51, 84, 42, 29, 43, 29, 
                -124, 3, 1, 51, 84, -89, 0, 75, 42, 29, 43, 29, -124, 3, 1, 51, 84, 42, 29, 43, 29, -124, 3, 1, 51, 84, 
                42, 29, 43, 29, -124, 3, 1, 51, 84, 42, 29, 43, 29, -124, 3, 1, 51, 84, 42, 29, 43, 29, -124, 3, 1, 51, 
                84, 42, 29, 43, 29, -124, 3, 1, 51, 84, 42, 29, 43, 29, -124, 3, 1, 51, 84, 42, 29, 43, 29, -124, 3, 1, 
                51, 84, 29, 28, -95, -1, -74, -79, 0, 0, 0, 2, 0, 10, 0, 0, 0, 86, 0, 21, 0, 0, 0, 3, 0, 3, 0, 4, 0, 5, 
                0, 5, 0, 56, 0, 7, 0, 65, 0, 8, 0, 74, 0, 9, 0, 83, 0, 10, 0, 92, 0, 11, 0, 101, 0, 12, 0, 110, 0, 13, 
                0, 119, 0, 16, 0, 122, 0, 17, 0, -125, 0, 18, 0, -116, 0, 19, 0, -107, 0, 20, 0, -98, 0, 21, 0, -89, 0, 
                22, 0, -80, 0, 23, 0, -71, 0, 24, 0, -62, 0, 16, 0, -57, 0, 26, 0, 11, 0, 0, 0, 42, 0, 4, 0, 0, 0, -56, 
                0, 16, 0, 17, 0, 0, 0, 0, 0, -56, 0, 18, 0, 17, 0, 1, 0, 3, 0, -59, 0, 19, 0, 20, 0, 2, 0, 5, 0, -61, 
                0, 21, 0, 20, 0, 3, 0, 1, 0, 22, 0, 0, 0, 2, 0, 23};
        return defineClass(name, b, 0, b.length);
    }

    public static void main(String[] args) throws Exception {
        byte[] to = new byte[100];
        byte[] from = new byte[100];
        for (int i = 0; i < from.length; i++)
            from[i] = (byte)i;
        Method[] ms = new Sample().loadClass("Copy").getMethods();
        ms[0].invoke(null, to, from);
        System.out.println(java.util.Arrays.toString(to));
    }
}

[ Java ] [ download code ] ]

SiroKuro's comment on 疑似並行処理

疑似並行処理 (Nested Flatten)

java.util.concurrent.* ベースで作りました。切り替えは単純に Thread.yield() しようかと思ったんですが、程よく混ざらないので「いっせ～の、せ！」で実行させるために無駄に CyclicBarrier です。

import java.util.concurrent.*;
public class test {
    public static void main(String[] args) {
        ExecutorService executor = Executors.newCachedThreadPool();
        final CyclicBarrier barrier = new CyclicBarrier(2);
        try {
            // その１
            executor.submit(new Callable<Object>(){
                public Object call() throws Exception {
                    for(int i = 1; i <= 10; i++) {
                        barrier.await();
                        System.out.println(i);
                    }
                    return null;
                }
            });
            // その２
            executor.submit(new Callable<Object>(){
                public Object call() throws Exception {
                    for(char c = 'A'; c <= 'J'; c++) {
                        barrier.await();
                        System.out.println(c);
                    }
                    return null;
                }
            });
        }
        finally {
            executor.shutdown();
        }
    }
}

[ Java ] [ download code ] ]