com.dahuatech.hutool.core.collection.LineIter Maven / Gradle / Ivy

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package com.dahuatech.hutool.core.collection;

import com.dahuatech.hutool.core.io.IORuntimeException;
import com.dahuatech.hutool.core.io.IoUtil;
import com.dahuatech.hutool.core.lang.Assert;

import java.io.*;
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();
 * }
 * 
 *
 * 此类来自于Apache Commons io
 *
 * @author looly
 * @since 4.1.1
 */
public class LineIter implements Iterator, Iterable, Closeable, Serializable {
  private static final long serialVersionUID = 1L;

  /** 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 (false == 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;
  }
}