文件读写

wade6 · wade6 · commit 892fcd434355 · 2018-04-19T00:25:30.000+08:00
diff --git a/fileInputStream.txt b/fileInputStream.txt
@@ -0,0 +1,26 @@
+hello world!hello world!hello world!hello world!hello world!hello world!hello world!hello world!
+读文件
+hello world!hello world!hello world!hello world!hello world!hello world!hello world!hello world!
+读文件
+hello world!hello world!hello world!hello world!hello world!hello world!hello world!hello world!
+读文件
+hello world!hello world!hello world!hello world!hello world!hello world!hello world!hello world!
+读文件
+hello world!hello world!hello world!hello world!hello world!hello world!hello world!hello world!
+读文件
+hello world!hello world!hello world!hello world!hello world!hello world!hello world!hello world!
+读文件
+hello world!hello world!hello world!hello world!hello world!hello world!hello world!hello world!
+读文件
+hello world!hello world!hello world!hello world!hello world!hello world!hello world!hello world!
+读文件
+hello world!hello world!hello world!hello world!hello world!hello world!hello world!hello world!
+读文件
+hello world!hello world!hello world!hello world!hello world!hello world!hello world!hello world!
+读文件
+hello world!hello world!hello world!hello world!hello world!hello world!hello world!hello world!
+读文件
+hello world!hello world!hello world!hello world!hello world!hello world!hello world!hello world!
+读文件
+hello world!hello world!hello world!hello world!hello world!hello world!hello world!hello world!
+读文件
diff --git a/fileOutputStream.txt b/fileOutputStream.txt
@@ -0,0 +1,2 @@
+hello world! 写文件
+写文件 hello world! 
diff --git a/src/main/java/com/code/repository/charset/CharAndByteDemo.java b/src/main/java/com/code/repository/charset/CharAndByteDemo.java
@@ -0,0 +1,38 @@
+package com.code.repository.charset;
+
+/**
+ * char 和 byte的关系
+ * @author hm
+ *
+ */
+public class CharAndByteDemo {
+
+	public static void main(String[] args) {
+		char a = 'a';
+		byte[] b = CharAndByteDemo.charToByte(a);
+		System.out.println(b[0]);
+		System.out.println(b[1]);
+	}
+	
+	/**
+	 * 字符char转换成byte
+	 * 
+	 * 首先要明白的是：
+	 * 	byte是字节数据类型，由8位二进制组成；
+	 * 	char是字符数据类型，占2个字节byte；
+	 *  
+	 * @param c
+	 * @return
+	 */
+	public static byte[] charToByte(char c) {
+		byte[] b = new byte[2];// 一个字符是2个字节，所以b的长度为2
+		b[0] = (byte)((c & 0xFF00) >> 8);// 0xff00 为 1111 1111 0000 0000
+		b[1] = (byte)(c & 0xff); // 0xff为 1111 1111
+		return b;
+	}
+	
+	public static char byteToChar(byte[] b) {
+		char c = (char)(((b[0] & 0xff) << 8)|(b[1] & 0xff));
+		return c;
+	}
+}
diff --git a/src/main/java/com/code/repository/charset/StringAndChar.java b/src/main/java/com/code/repository/charset/StringAndChar.java
@@ -2,6 +2,13 @@
 
 import java.io.UnsupportedEncodingException;
 
+/**
+ * String 内部默认utf-16编码,unicode字符集，2字节;
+ * 用char数组存储，一个char占2个字节;
+ * String.length返回的是char数组的长度
+ * @author hm
+ *
+ */
 public class StringAndChar {
 	
 	static String GBK = "GBK";
@@ -15,16 +22,23 @@ public class StringAndChar {
 	public static void main(String[] args) throws UnsupportedEncodingException {
 		String str = new String("中"); // 汉字，GBK、unicode是2个字节；utf-8是3个字节，文件默认是UTF-8编码
 		
+		System.out.println("default:"+str.getBytes().length);// 默认是utf-8，输出3
+		
+		System.out.println("change ot GBK:"+new String (str.getBytes("GBK"),"GBK"));
+		
 		byte[] bit_utf_8 = str.getBytes(UTF8);
 		System.out.println("utf-8:"+bit_utf_8.length);// 输出字节长度，utf-8编码多字节编码，汉字是3个，所以输出3
 		
 		for(byte b : bit_utf_8) {
 			System.out.println( Integer.toBinaryString((b & 0xFF) + 0x100).substring(1));
 		}
 		
-		// 把这个utf-8的字节转换成string
+		
+		/**
+		 * 把这个utf-8的字节转换成string,3个字节变成2个字节，看源码实现
+		 */
 		String strFromUtf8 = new String(bit_utf_8);
-		System.out.println("strFromUtf8:"+strFromUtf8 +" length:"+strFromUtf8.length());
+		System.out.println("strFromUtf8:"+strFromUtf8 +" length:"+strFromUtf8.length());// String 内部默认utf-16编码，用char数组存储，一个char占2个字节，输出的长度为数组长度，所以为1
 		
 		byte[] bit_GBK = str.getBytes(GBK);
 		System.out.println("gbk:"+bit_GBK.length);// 输出字节长度，gbk编码2个字节编码，所以输出2
diff --git a/src/main/java/com/code/repository/io/AutoColseableTest.java b/src/main/java/com/code/repository/io/AutoColseableTest.java
@@ -0,0 +1,28 @@
+package com.code.repository.io;
+
+public class AutoColseableTest {
+
+	public static void main(String[] args) {
+		try(MyResource my = new MyResource()) {
+			my.invoke();
+		} catch (Exception e) {
+		}
+		System.out.println("end");
+	}
+	
+	// 资源自动关闭的接口AutoCloseable
+	// 在使用的时候只需要把资源在try块中用小括号括起来就可以了
+	static class MyResource implements AutoCloseable{
+		@Override
+		public void close() throws Exception {
+			System.out.println("i am closed!");
+			
+		}
+		
+		public void invoke() {
+			System.out.println("i am working!");
+		}
+	}
+
+}
+
diff --git a/src/main/java/com/code/repository/io/FileInputStreamTest.java b/src/main/java/com/code/repository/io/FileInputStreamTest.java
@@ -0,0 +1,33 @@
+package com.code.repository.io;
+
+import java.io.FileInputStream;
+import java.io.IOException;
+
+/**
+ * 
+ * @author hm
+ *
+ */
+public class FileInputStreamTest {
+
+	public static void main(String[] args) throws IOException {
+		FileInputStream fis = null;
+		try {
+			// 创建字节文件输入流
+			fis = new FileInputStream("fileInputStream.txt");
+			// 最多读64字节
+			byte[] b = new byte[64];
+			// 实际读取字节数
+			int len = 0;
+			// 循环读取并输出
+			while((len=fis.read(b)) > 0) {
+				System.out.print(new String(b,0,len)+"|");//注意： 读取后，对中文转换有乱码问题
+			}
+		} catch (Exception e) {
+			e.printStackTrace();
+		} finally {
+			fis.close();
+		}
+		
+	}
+}
diff --git a/src/main/java/com/code/repository/io/FileOutputStreamTest.java b/src/main/java/com/code/repository/io/FileOutputStreamTest.java
@@ -0,0 +1,29 @@
+package com.code.repository.io;
+
+import java.io.FileNotFoundException;
+import java.io.FileOutputStream;
+import java.io.IOException;
+
+public class FileOutputStreamTest {
+
+	public static void main(String[] args) throws IOException {
+		FileOutputStream fos = null;
+		
+		try {
+			fos = new FileOutputStream("fileOutputStream.txt");
+			String str = "hello world! 写文件";
+			String str2 = "写文件 hello world! ";
+			fos.write(str.getBytes());
+			fos.write('\n');
+			fos.write(str2.getBytes());
+			System.out.println("ok");
+		} catch (FileNotFoundException e) {
+			// TODO Auto-generated catch block
+			e.printStackTrace();
+		} finally {
+			fos.close();
+		}
+		
+		
+	}
+}
diff --git a/src/main/java/com/code/repository/io/FileReaderTest.java b/src/main/java/com/code/repository/io/FileReaderTest.java
@@ -0,0 +1,25 @@
+package com.code.repository.io;
+
+import java.io.FileReader;
+import java.io.IOException;
+
+public class FileReaderTest {
+
+	public static void main(String[] args) throws IOException {
+		FileReader fr = null;
+		try{
+			// 创建字符文件输入流
+			fr = new FileReader("fileInputStream.txt");
+			// 每次读取128个字符
+			char[] b = new char[128];
+			int len;
+			// 循环读取
+			while((len = fr.read(b)) > 0) {
+				System.out.print(new String(b,0,len));
+			}
+		}catch (Exception e) {
+		}finally {
+			fr.close();
+		}
+	}
+}
diff --git a/src/main/java/com/code/repository/io/InputStreamReaderTest.java b/src/main/java/com/code/repository/io/InputStreamReaderTest.java
@@ -0,0 +1,30 @@
+package com.code.repository.io;
+
+import java.io.BufferedReader;
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.io.InputStreamReader;
+
+// 转换流
+public class InputStreamReaderTest {
+
+	public static void main(String[] args) throws IOException {
+		// 字节流转换成reader字符流
+		InputStreamReader reader = new InputStreamReader(new FileInputStream("fileInputStream.txt"));
+		// 包装成reader字符缓冲流
+		BufferedReader br = new BufferedReader(reader);
+		String str = null;
+		
+		try {
+			// 读取每一行打印
+			while((str = br.readLine())!=null) {
+				System.out.println(str);
+			}
+		} catch (IOException e) {
+			// TODO Auto-generated catch block
+			e.printStackTrace();
+		} finally {
+			br.close();
+		}
+	}
+}

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,2 @@`
	`1`	`+hello world! 写文件`
	`2`	`+写文件 hello world!`