JAVA基础知识之IO——Java IO体系及常用类

  1 package io;
  2 
  3 import java.io.BufferedReader;
  4 import java.io.FileInputStream;
  5 import java.io.FileNotFoundException;
  6 import java.io.FileOutputStream;
  7 import java.io.FileReader;
  8 import java.io.IOException;
  9 import java.io.InputStreamReader;
 10 import java.io.PrintStream;
 11 import java.io.PushbackReader;
 12 import java.io.StringReader;
 13 import java.io.StringWriter;
 14 
 15 public class TestIO {
 16     public static void printStream() throws FileNotFoundException, IOException {
 17         try (
 18                 FileOutputStream fos = new FileOutputStream("tmp.txt");
 19                 PrintStream ps = new PrintStream(fos)) {
 20             ps.println("普通字符串\n");
 21             //输出对象
 22             ps.println(new TestIO());
 23         } catch (IOException e) {
 24             e.printStackTrace();
 25         }
 26         System.out.println("输出完成");
 27                 
 28     }
 29     public static void stringNode() throws IOException {
 30         String str = "天王盖地虎\n"
 31                 + "宝塔镇河妖\n";
 32         char[] buf = new char[32];
 33         int hasRead = 0;
 34         //StringReader将以String字符串为节点读取数据
 35         try (StringReader sr = new StringReader(str)) {
 36             while ((hasRead = sr.read(buf)) > 0) {
 37                 System.out.print(new String(buf, 0, hasRead));
 38             }
 39         } catch (IOException e) {
 40             e.printStackTrace();
 41         }
 42         
 43         //由于String是一个不可变类，因此创建StringWriter时，实际上是以一个StringBuffer作为输出节点
 44         try (StringWriter sw = new StringWriter()) {
 45             sw.write("黑夜给了我黑色的眼睛\n");
 46             sw.write("我却用它寻找光明\n");
 47             //toString()返回sw节点内的数据
 48             System.out.println(sw.toString());
 49         } catch (IOException e) {
 50             e.printStackTrace();
 51         }
 52     }
 53     
 54     public static void keyIn() throws IOException {
 55         try (
 56                 //InputStreamReader是从byte转成char的桥梁
 57                 InputStreamReader reader = new InputStreamReader(System.in);
 58                 //BufferedReader(Reader in)是char类型输入的包装类
 59                 BufferedReader br = new BufferedReader(reader);
 60                 ) {
 61             String line = null;
 62             while ((line = br.readLine()) != null) {
 63                 if (line.equals("exit")) {
 64                     //System.exit(1);
 65                     break;
 66                 }
 67                 System.out.println(line);
 68             }
 69         } catch (IOException e) {
 70             e.printStackTrace();
 71         }
 72     }
 73     
 74     public static void pushback() throws FileNotFoundException, IOException {
 75         try (PushbackReader pr = new PushbackReader(new FileReader("C:/PROJECT/JavaBasic/PROJECT_JavaBasic/src/io/TestIO.java"),64)) {
 76             char[] buf = new char[32];
 77             String lastContent = "";
 78             int hasRead = 0;
 79             while ((hasRead = pr.read(buf)) > 0) {
 80                 String content = new String(buf, 0, hasRead);
 81                 int targetIndex = 0;
 82                 if ((targetIndex = (lastContent + content).indexOf("targetIndex = (lastContent + content)")) > 0) {
 83                     pr.unread((lastContent + content).toCharArray());
 84                     if (targetIndex > 32) {
 85                         buf = new char[targetIndex];
 86                     }
 87                     pr.read(buf , 0 , targetIndex);
 88                     System.out.println(new String(buf, 0 , targetIndex));
 89                     System.exit(0);
 90                 } else {
 91                     System.out.println(lastContent);
 92                     lastContent = content;
 93                 }
 94             }
 95         } catch (IOException e) {
 96             e.printStackTrace();
 97         }
 98     }
 99     
100     public static void main(String[] args) throws IOException {
101         printStream();
102         //stringNode();
103         //keyIn();
104         //pushback();
105     }
106 }