BufferedReaderのIterableラッパー. 最終行の判定ができるのでCSVのヘッダーやフッターをとるのに便利.

ReaderIterator.java

package utils;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.Reader;
import java.util.Iterator;

/**
 * BufferedReader Iterable Wrapper.
 * 
 * @author koduki
 *
 */
public class ReaderIterator implements Iterator<String>, Iterable<String> {
	private BufferedReader bufferedReader;
	private String line;
	private boolean doneNext = false;
	private int firstCheckCounter = 0;

	/**
	 * constructor.
	 * @param reader target reader.
	 */
	public ReaderIterator(BufferedReader bufferedReader) {
		super();
		this.bufferedReader = bufferedReader;
	}

	/**
	 * constructor.
	 * @param reader target reader.
	 */
	public ReaderIterator(Reader reader) {
		this(new BufferedReader(reader));
	}

	@Override
	public boolean hasNext() {
		boolean result = false;
		try {
			if (!this.doneNext) {
				this.line = this.bufferedReader.readLine();
				this.doneNext = true;
			}
			result = (line != null);

		} catch (IOException e) {
			return false;
		}
		return result;
	}

	@Override
	public String next() {
		String result = null;
		if (this.hasNext()) {
			result = this.line;
		}
		this.doneNext = false;
		if (firstCheckCounter <= 1) {
			this.firstCheckCounter += 1;
		}
		return result;
	}

	@Override
	public void remove() {
		throw new UnsupportedOperationException();
	}

	/**
	 * return this instance.
	 * @return this instance.
	 */
	@Override
	public Iterator<String> iterator() {
		return this;
	}

	/**
	 * if first line, return true.
	 * @return true is first line.
	 */
	public boolean isFirst() {
		return (firstCheckCounter == 1);
	}

	/**
	 * if last line, return true.
	 * @return true is last line.
	 */
	public boolean isLast() {
		return (this.hasNext() == false);
	}
}

ReaderIteratorTest.java

package utils;

import static org.junit.Assert.*;

import java.io.BufferedReader;
import java.io.StringReader;
import java.util.Arrays;
import java.util.Iterator;

import org.junit.Test;

public class ReaderIteratorTest {

	@Test
	public void testIterator() {
		BufferedReader br = new BufferedReader(new StringReader("header\nbody1\nbody2\nfooter"));
		Iterator<String> expecteds = Arrays.asList("header", "body1", "body2","footer").iterator();

		for (ReaderIterator iterator = new ReaderIterator(br); iterator.hasNext();) {
			assertEquals(expecteds.next(), iterator.next());
		}
		assertFalse(expecteds.hasNext());
	}

	@Test
	public void testIterable() {
		BufferedReader br = new BufferedReader(new StringReader("header\nbody1\nbody2\nfooter"));
		Iterator<String> expecteds = Arrays.asList("header", "body1", "body2", "footer").iterator();
		ReaderIterator iterator = new ReaderIterator(br);
		for (String line : iterator) {
			assertEquals(expecteds.next(), line);
		}
		assertFalse(expecteds.hasNext());
	}

	@Test
	public void testHeaderAndFooter() {
		boolean doneFirst = false;
		boolean doneLast = false;
		Iterator<String> expecteds = Arrays.asList("body1", "body2").iterator();
		ReaderIterator iterator = new ReaderIterator(new StringReader("header\nbody1\nbody2\nfooter"));
		for (String line : iterator) {
			if (iterator.isFirst()) {
				assertEquals("header", line);
				doneFirst = true;
			} else if (iterator.isLast()) {
				assertEquals("footer", line);
				doneLast = true;
			} else {
				assertEquals(expecteds.next(), line);
			}
		}

		assertFalse(expecteds.hasNext());
		assertTrue(doneFirst);
		assertTrue(doneLast);
	}
}