CloseableUtility.java

package com.kanasansoft.CloseableUtility;

import java.io.Closeable;
import java.io.IOException;
import java.util.Arrays;
import java.util.List;

public abstract class CloseableUtility {

	public CloseableUtility(Closeable... closeables) throws IOException {

		main(closeables);
		closeAll(closeables);

	}

	abstract public void main(Closeable... closeables) throws IOException;

	private void closeAll(Closeable... closeables) throws IOException {

		closeAll(Arrays.asList(closeables));

	}

	private void closeAll(List<Closeable> closeables) throws IOException {

		if (closeables.isEmpty()) {
			return;
		}

		try {
			if (closeables.get(0) != null) {
				closeables.get(0).close();
			}
		} catch (IOException e) {
			throw e;
		} finally {
			closeAll(closeables.subList(1, closeables.size()));
		}

	}

}

gistfile1.md

Streamを安全にcloseするためのアイディア その2

概要

インスタンス化時に渡されたストリームが、mainメソッドに渡される (Rubyのイテレータに近い)

欠点

• キャストがキモい

Usage.java

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.Closeable;
import java.io.IOException;

import com.kanasansoft.CloseableUtility.CloseableUtility;

public class Usage {

	public static void main(String[] args) {
		new Usage();
	}

	public Usage() {

		ByteArrayInputStream is1 = new ByteArrayInputStream(new byte[]{});
		ByteArrayInputStream is2 = new ByteArrayInputStream(new byte[]{});
		ByteArrayOutputStream os1 = new ByteArrayOutputStream();
		ByteArrayOutputStream os2 = new ByteArrayOutputStream();

		try {
			new CloseableUtility(is1, is2, os1, os2){
				@Override
				public void main(Closeable... closeables) throws IOException {
					ByteArrayInputStream is1 = (ByteArrayInputStream) closeables[0];
					ByteArrayInputStream is2 = (ByteArrayInputStream) closeables[1];
					ByteArrayOutputStream os1 = (ByteArrayOutputStream) closeables[2];
					ByteArrayOutputStream os2 = (ByteArrayOutputStream) closeables[3];
					//ex.
					//is1.read();
					//is2.read();
					//os1.write(new byte[]{});
					//os2.write(new byte[]{});
					//omit
				}
			};
		} catch (IOException e) {
			e.printStackTrace();
		}

	}

}