java_IO流之FileInputStream和FileOutputStream

看，API說的多簡單啊：

FileInputStream 用於讀取諸如圖像數據之類的原始字節流。要讀取字符流，請考慮使用 FileReader。

FileOutputStream 用於寫入諸如圖像數據之類的原始字節的流。要寫入字符流，請考慮使用 FileWriter。 

FileInputStream與FileOutputStream都是字節流，所以它們都是用來讀byte與寫byte的。

上例子：

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

public class FileStreamTest {

	public static void main(String[] args) {
		// writeTest();
		// readTest_1();
		// readTest_2();
		// readTest_3();
		// copyFile();
	}

	// 用字節流文件的讀寫。
	private static void copyFile() {
		FileInputStream fis = null;
		FileOutputStream fos = null;
		try {
			fis = new FileInputStream("F:\\library.rar");
			fos = new FileOutputStream("F:\\library_copy.rar");
			byte[] buf = new byte[1024];
			int len = 0;
			while ((len = fis.read(buf)) != -1) {
				fos.write(buf, 0, len);
			}
			System.out.println("複製完成");
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		} finally {
			try {
				if (fis != null) {
					fis.close();
				}
			} catch (IOException e) {
				e.printStackTrace();
			}
			try {
				if (fos != null) {
					fos.close();
				}
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
	}

	private static void readTest_3() {
		FileInputStream fis = null;
		try {
			fis = new FileInputStream("D:\\log.txt");
			// available()方法是用於創建一個大小剛剛適合的緩衝區，不過如果資源文件過大的話，很容易造成內在溢出的問題。
			byte[] buf = new byte[fis.available()];
			fis.read(buf);
			System.out.println(new String(buf));
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		} finally {
			try {
				if (fis != null) {
					fis.close();
				}
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
	}

	private static void readTest_2() {
		FileInputStream fis = null;
		try {
			fis = new FileInputStream("D:\\log.txt");
			byte[] buf = new byte[1024];
			int len = 0;
			while ((len = fis.read(buf)) != -1) {
				System.out.println(new String(buf, 0, len));
			}
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		} finally {
			try {
				if (fis != null) {
					fis.close();
				}
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
	}

	private static void readTest_1() {
		FileInputStream fis = null;
		try {
			fis = new FileInputStream("D:\\log.txt");
			int b = 0;
			while ((b = fis.read()) != -1) {
				System.out.println((char) b);
			}
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		} finally {
			try {
				if (fis != null) {
					fis.close();
				}
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
	}

	private static void writeTest() {
		FileOutputStream fos = null;
		try {
			fos = new FileOutputStream("D:\\log.txt");
			// 字節流操作的是字節數組。字符流操作的是字符數組。
			fos.write("abcdefg".getBytes());
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		} finally {
			try {
				if (fos != null) {
					fos.close();
				}
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
	}
}