java学习笔记一 2019.6.18 周二 三亚 特别热

一、OutputStream write import java.io.File; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; import java.io.OutputStream;

public class StreamTest2 {

public static void main(String[] args) {
	// TODO Auto-generated method stub
	//File file=new File("/Users/hanzhao/Desktop/zhaohanhan.txt");
	//System.out.println(file.exists());
	
	//题外话
	String s="aa我";
	System.out.println(s.length());//返回3个字符char
	byte[]bytes1=s.getBytes();
	System.out.println(bytes1.length);//返回5个字节，一个字母一个字节，一个汉字两个字节
	
	//FileOutputStream fos = null;//局部变量要赋值
	OutputStream fos = null;//用FileOutputStream 的父类来调用，OutputStream是abstract抽象类，不能new
	try {
//	fos = new FileOutputStream("/Users/hanzhao/Desktop/zhaohanhan.txt");
	fos=new FileOutputStream("/Users/hanzhao/Desktop/daleilei.txt");
	byte[] bytes="aaa找找找adfsdfsdfads的房间都是法律框架上的六块腹肌都是".getBytes();//String类里面的方法，返回byte【】
	fos.write(bytes);
	//fos.close();//如果前面的代码出现问题，那么fos.close();就不会被执行，所以，把这个方法写在finally，保障一定被执行
	//不执行的话，会占用资源，执行一次占用一次
	}catch(FileNotFoundException e) {
		System.out.println("找不到文件");
	}catch(IOException ex) {
		System.out.println("找不到文件流");
	}finally {
		if(fos!=null) {
			try {
			fos.close();
			}catch(IOException e) {
				//里面可以不写，耍流氓啊啊啊啊啊啊
			}
		}
	}  //结果就是daleilei.txt被写入内容

}

}

二、InputStream read import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.IOException; import java.io.InputStream;

public class StreamTest1 {

public static void main(String[] args) {
	// TODO Auto-generated method stub
	InputStream fis = null;
	try {
		fis = new FileInputStream("/Users/hanzhao/Desktop/xiaoshuo.txt");
		//xiaoshuo.txt里面已经放好了内容，把这些内容read到console控制台里面
		byte[] bytes = new byte[50];
		/*int b=fis.read(bytes);//返回值int，代表每次读的字节数
		System.out.println(b);//每次读50个字节
		System.out.println(bytes);//[B@79698539
		System.out.println(new String(bytes));
		//要把read的bytes字节转换为String数据,但是这样只能read到50个字节的内容，所有我们要用while循环以下
		*/
		while(fis.read(bytes)>0) {//如果写成fis.read()>0，显示为一片空白
			String s=new String(bytes);
			System.out.print(s);
			System.out.println(s);
		}//read成功，但是有乱码，这是因为读取字节流，按每次50个字节读，有可能会read到半个汉字的原因。
		
		

	} catch (FileNotFoundException e) {
		// TODO Auto-generated catch block
		System.out.println("文件地址不对");
		// e.printStackTrace();
	} catch (IOException e) {
		System.out.println("read❌");
	} finally {
		if (fis != null) {
			try {
				fis.close();
			} catch (IOException e) {
				// TODO Auto-generated catch block
				// e.printStackTrace();
			}
		}
	}

}

} 三、字节流，read and write
// 没有调用IOUtils中的copy方法，老老实实自己写 import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream;

public class StreamTest3 {

public static void main(String[] args) {
	// TODO Auto-generated method stub
    long startMS = System.currentTimeMillis();
	InputStream fis = null;
	OutputStream fos = null;
	try {
		fis = new FileInputStream("/Users/hanzhao/Desktop/zhaizhai.txt");
		fos = new FileOutputStream("/Users/hanzhao/Desktop/xiaofengfeng.txt");
		byte[] bytes = new byte[1204];
		int len;
		while ((len = fis.read(bytes)) > 0) {
			fos.write(bytes, 0, len);
		}

		long endMS = System.currentTimeMillis();
		System.out.println("copytime is" + (endMS - startMS));

	} catch (FileNotFoundException e) {
		// TODO Auto-generated catch block
		// e.printStackTrace();
		System.out.println("file is not exist" + e.getMessage());

	} catch (IOException e) {
		// TODO Auto-generated catch block
		// e.printStackTrace();
		System.out.println();
	} finally {
		IOUtils.closeQuietly(fis);
		IOUtils.closeQuietly(fos);
	}


}

}

四、调用了IOUtils中的方法了 import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream;

public class StreamTest5 {

public static void main(String[] args) {
	
	//调用了IOUtils中的方法了
    long startMS = System.currentTimeMillis();
	InputStream fis = null;
	OutputStream fos = null;
	try {
		fis = new FileInputStream("/Users/hanzhao/Desktop/zhaizhai.txt");
		fos = new FileOutputStream("/Users/hanzhao/Desktop/xiaofengfeng.txt");
		/*byte[] bytes = new byte[1204];
		int len;
		while ((len = fis.read(bytes)) > 0) {
			fos.write(bytes, 0, len);
		}*/
		IOUtils.copy(fis, fos);

		long endMS = System.currentTimeMillis();
		System.out.println("copytime is" + (endMS - startMS));

	} catch (FileNotFoundException e) {
		// TODO Auto-generated catch block
		// e.printStackTrace();
		System.out.println("file is not exist" + e.getMessage());

	} catch (IOException e) {
		// TODO Auto-generated catch block
		// e.printStackTrace();
		System.out.println();
	} finally {
		IOUtils.closeQuietly(fis);
		IOUtils.closeQuietly(fos);
	}


}

//自己写的copy方法，好搞笑写的，太×××烂啦，怎么想的，int bufferSize明明指的是1024等等数值，我怎么把它想成返回值了 //还有，公式不是万能的啊，明明只能代替下面这些，我怎么全写上了，服了，服了。。。。。。 // byte[] bytes = new byte[1204]; // int buffSize1; // while ((buffSize1 = inStream1.read(bytes)) > 0) { // outStream1.write(bytes, 0, buffSize1); // } //copy方法放在IUOtils类里面了，方便一些存放和调用 public static void copy(InputStream inStream, OutputStream outStream, int bufferSize) {

	InputStream inStream1 = null;
	OutputStream outStream1 = null;
	try {
		inStream1 = new FileInputStream("/Users/hanzhao/Desktop/zhaizhai.txt");
		outStream1 = new FileOutputStream("/Users/hanzhao/Desktop/xiaofengfeng.txt");
		byte[] bytes = new byte[1204];
		int buffSize1;
		while ((buffSize1 = inStream1.read(bytes)) > 0) {
			outStream1.write(bytes, 0, buffSize1);
		}

	} catch (FileNotFoundException e) {
		// TODO Auto-generated catch block
		// e.printStackTrace();
		System.out.println("file is not exist" + e.getMessage());

	} catch (IOException e) {
		// TODO Auto-generated catch block
		// e.printStackTrace();
		System.out.println();
	} finally {
		IOUtils.closeQuietly(inStream1);
		IOUtils.closeQuietly(outStream1);
	}

}

}

五、IOUtils类，Utils意思为工具类，里面存放的全部是static静态方法 import java.io.Closeable; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.io.Reader; import java.io.Writer;

public class IOUtils {

// IOUtils utils代表工具类，里面是static类
// InputStream OutputStream Reader Writer都implements Closeable
// 所以都可以调用close();方法，体现了不同对象的多态

public static void closeQuietly(InputStream inStream) {
	if (inStream != null) {
		try {
			inStream.close();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}

public static void closeQuietly(OutputStream outStream) {
	if (outStream != null) {
		try {
			outStream.close();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}

public static void closeQuietly(Reader reader) {
	if (reader != null) {
		try {
			reader.close();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}

public static void closeQuietly(Writer writer) {
	if (writer != null) {
		try {
			writer.close();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}

public static void closeQuietly(Closeable closeable) {
	if (closeable != null) {
		try {
			closeable.close();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}

public static void copy(InputStream inStream, OutputStream outStream, int bufferSize) throws IOException {
	// 程序要严谨，要判断inStream，outStream如果==null，bufferSize如果小于等于0，都要抛出异常
	if (inStream == null) {
		throw new IllegalArgumentException("inStream不能为空");
		// IllegalArgumentException extends RuntimeException   把异常抛出去 由调用着处理
	}
	if (outStream == null) {
		throw new IllegalArgumentException("outStream不能为空");
	}
	if (bufferSize <= 0) {
		throw new IllegalArgumentException("bufferSize不能为负数");
	}
	byte[] buffer = new byte[bufferSize];
	int len;
	while ((len = inStream.read(buffer)) > 0) {// 把异常抛出去 由调用着处理
		outStream.write(buffer, 0, len);
	}
}

public static void copy(InputStream inStream, OutputStream outStream) throws IOException{
	copy(inStream, outStream, 1024*1024);//把异常抛出去，由调用着处理
} 

}

六、自己写着实验用的IOUtils import java.io.Closeable; import java.io.IOException;

public class IOUtils2 implements Closeable {

public IOUtils2() {
	super();
	// TODO Auto-generated constructor stub
}

@Override
public void close() throws IOException {
	// TODO Auto-generated method stub
	
}

}

七、自己写着实验用的IOUtils

import java.io.Closeable; import java.io.IOException;

public interface IOUtils3 extends Closeable{

@Override
default void close() throws IOException {
	// TODO Auto-generated method stub
	
}

}

总结；要敢于犯错，在错误中总结经验。