com.github.zhangxd1989.basetool.collection.LineIter Maven / Gradle / Ivy
package com.github.zhangxd1989.basetool.collection;
import com.github.zhangxd1989.basetool.io.IORuntimeException;
import com.github.zhangxd1989.basetool.io.IoUtil;
import com.github.zhangxd1989.basetool.lang.Assert;
import java.io.BufferedReader;
import java.io.Closeable;
import java.io.IOException;
import java.io.InputStream;
import java.io.Reader;
import java.nio.charset.Charset;
import java.util.Iterator;
import java.util.NoSuchElementException;
/**
* 将Reader包装为一个按照行读取的Iterator
* 此对象遍历结束后，应关闭之，推荐使用方式:
*
* LineIterator it = null;
* try {
* it = new LineIterator(reader);
* while (it.hasNext()) {
* String line = it.nextLine();
* // do something with line
* }
* } finally {
* it.close();
* }
*
*
* @author sheldon
*/
public class LineIter implements Iterator, Iterable, Closeable {
/**
* The reader that is being read.
*/
private final BufferedReader bufferedReader;
/**
* The current line.
*/
private String cachedLine;
/**
* A flag indicating if the iterator has been fully read.
*/
private boolean finished = false;
/**
* 构造
*
* @param in {@link InputStream}
* @param charset 编码
* @throws IllegalArgumentException reader为null抛出此异常
*/
public LineIter(InputStream in, Charset charset) throws IllegalArgumentException {
this(IoUtil.getReader(in, charset));
}
/**
* 构造
*
* @param reader {@link Reader}对象，不能为null
* @throws IllegalArgumentException reader为null抛出此异常
*/
public LineIter(Reader reader) throws IllegalArgumentException {
Assert.notNull(reader, "Reader must not be null");
this.bufferedReader = IoUtil.getReader(reader);
}
/**
* 判断{@link Reader}是否可以存在下一行。 If there is an IOException then {@link #close()} will be called on this instance.
*
* @return {@code true} 表示有更多行
* @throws IORuntimeException IO异常
*/
@Override
public boolean hasNext() throws IORuntimeException {
if (cachedLine != null) {
return true;
} else if (finished) {
return false;
} else {
try {
while (true) {
String line = bufferedReader.readLine();
if (line == null) {
finished = true;
return false;
} else if (isValidLine(line)) {
cachedLine = line;
return true;
}
}
} catch (IOException ioe) {
close();
throw new IORuntimeException(ioe);
}
}
}
/**
* 返回下一行内容
*
* @return 下一行内容
* @throws NoSuchElementException 没有新行
*/
@Override
public String next() throws NoSuchElementException {
return nextLine();
}
/**
* 返回下一行
*
* @return 下一行
* @throws NoSuchElementException 没有更多行
*/
public String nextLine() throws NoSuchElementException {
if (!hasNext()) {
throw new NoSuchElementException("No more lines");
}
String currentLine = this.cachedLine;
this.cachedLine = null;
return currentLine;
}
/**
* 关闭Reader
*/
@Override
public void close() {
finished = true;
IoUtil.close(bufferedReader);
cachedLine = null;
}
/**
* 不支持移除
*
* @throws UnsupportedOperationException 始终抛出此异常
*/
@Override
public void remove() {
throw new UnsupportedOperationException("Remove unsupported on LineIterator");
}
/**
* 重写此方法来判断是否每一行都被返回，默认全部为true
*
* @param line 需要验证的行
* @return 是否通过验证
*/
protected boolean isValidLine(String line) {
return true;
}
@Override
public Iterator iterator() {
return this;
}
}