Java第十九天（字節流和字符流轉換、打印流、Properties類）

85.字符流和字節流轉換

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

public class OutputStreamWriterDemo {
    public static void main(String[] args) {
        //建立字符流轉換字節流的橋樑的對象
        OutputStreamWriter ow=null;
        try {
            //字符流通向字節流的橋樑能夠指定存儲的編碼
            ow=new OutputStreamWriter(new FileOutputStream("aa.txt"),"GBK");
            ow.write("加油");
            ow.flush();//操做視做字符流
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if(ow!=null){
                try {
                    ow.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;

public class InputStreamReaderDemo {
    public static void main(String[] args) {
        InputStreamReader ir=null;
        try {
            //寫出的時候指定的什麼編碼存儲，讀取的時候指定編碼解碼才能讀取，不然會讀取亂碼
            ir=new InputStreamReader(new FileInputStream("aa.txt"),"GBK");
            char[] cs=new char[1024];
            int len = ir.read(cs);
            System.out.println(new String(cs,0,len));
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if(ir!=null){
                try {
                    ir.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

通常開發工具默認是UTF-8編碼

86.打印流

 

import java.io.IOException;
import java.io.PrintWriter;

public class PrintWriterDemo {
    public static void main(String[] args) {
        PrintWriter pw=null;
        try {
            pw=new PrintWriter("bb.txt");
            pw.print("地球人都知道");
            pw.print(99);
            pw.print('a');
            pw.print(1.2f);
            pw.print(new char[]{'s','t','o'});
            pw.flush();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if(pw!=null){
                pw.close();
            }
        }
    }
}

import java.io.*;

public class PrintWriterDemo1 {
    public static void main(String[] args) {
        PrintWriter pw=null;
        BufferedReader reader=null;
        try {
            pw=new PrintWriter(System.out);
            reader=new BufferedReader(new FileReader("bb.txt"));
            //設置一個讀取的標識
            String s = null;
            while ((s=reader.readLine())!=null){
                pw.print(s);
                pw.flush();
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                if(reader!=null){
                    reader.close();
                }
                if(pw!=null){
                    pw.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

87.Properties類

特色：

1.繼承於Hashtable，是線程安全的鍵值對存儲結構

2. Properties 可保存在流中或從流中加載

3. 只能保存字符串的鍵值對。

import java.util.Properties;

public class PropertiesDemo {
    public static void main(String[] args) {
        //建立一個Properties
        Properties properties=new Properties();
        //成對存儲字符串
        properties.setProperty("001","張二蛋");
        properties.setProperty("002","張二瓜");
        properties.setProperty("003","張二狗");
        properties.setProperty("004","張二餅");
        System.out.println(properties);
//根據鍵獲取值
        String property = properties.getProperty("001");
        String property1 = properties.getProperty("002");
        String property2 = properties.getProperty("003");
        String property3 = properties.getProperty("004");
        System.out.println(property);
        System.out.println(property1);
        System.out.println(property2);
        System.out.println(property3);
    }
}

import java.io.PrintWriter;
import java.util.Properties;

public class PropertiesDemo1 {
    public static void main(String[] args) {
        //建立一個Properties
        Properties properties=new Properties();
        //成對存儲字符串
        properties.setProperty("001","張二蛋");
        properties.setProperty("002","張二瓜");
        properties.setProperty("003","張二狗");
        properties.setProperty("004","張二餅");
        //根據鍵獲取值
        String property = properties.getProperty("001");
        String property1 = properties.getProperty("002");
        String property2 = properties.getProperty("003");
        String property3 = properties.getProperty("004");
        //建立一個打印流
        PrintWriter printWriter=null;
        try {
            printWriter=new PrintWriter("cc.properties");
            //將properties寫出到printWriter
            properties.list(printWriter);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if(printWriter!=null){
                printWriter.close();
            }
        }
    }
}

import java.io.FileReader;
import java.io.IOException;
import java.io.Reader;
import java.util.Properties;

public class PropertiesDemo2 {
    public static void main(String[] args) {
        //建立一個Properties
        Properties properties=new Properties();
        //建立一個打印流
        Reader reader=null;
        try {
            reader=new FileReader("cc.properties");
            //從reader字符流中加載到屬性對象中
            properties.load(reader);
            System.out.println(properties);

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if(reader!=null){
                try {
                    reader.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

import java.io.*;
import java.util.Properties;

public class PropertiesDemo3 {
    public static void main(String[] args) {
        //建立一個Properties
        Properties properties=new Properties();
        //建立一個打印流
        Reader reader=null;
        PrintWriter writer=null;
        OutputStream out=null;
        try {
            //建立一個字符輸入流
            reader=new FileReader("cc.properties");
            //建立一個字符輸出流
            writer=new PrintWriter("dd.properties");
            //建立一個字節輸出流
            out=new FileOutputStream("ee.properties");
            //從reader字符流中加載到屬性對象中
            properties.load(reader);
            //再從屬性對象中寫出到writer
            properties.list(writer);
            writer.flush();
            //將屬性對象寫出到字節輸出流中並添加with store解釋
            properties.store(out,"with store");

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                if(reader!=null){
                    reader.close();
                }
                if(writer!=null){
                    writer.close();
                }
                if(out!=null){
                    out.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

實際工做中相對路徑不必定就是src目錄下，要訪問src目錄下文件方法參考以下

PropertiesDemo4.class.getClassLoader().getResourceAsStream("ee.properties")

import java.io.*;
import java.util.Properties;

public class PropertiesDemo4 {
    public static void main(String[] args) {
        //建立一個Properties
        Properties properties=new Properties();
        InputStream in=null;
        try {
            //建立一個字符輸入流,讀取的是與類同目錄下的src中的ee.properties
            in=PropertiesDemo4.class.getClassLoader().getResourceAsStream("ee.properties");
            //從reader字節流中加載到屬性對象中
            properties.load(in);
            System.out.println(properties);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {//
                if(in!=null) {
                    in.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}