Java 提供檔案基本套件都在java.io中,基本的管理檔案類別為 File 類別,可用來新增,刪除,檢查大小等等的功能,不過無法存取檔案內容,如下
1: package Test_IO;
2:
3: import java.io.*;//使用檔案套件必須先import套件類別
4:
5: public class Test_IO
6: { 7:
8: /**
9: * @param args
10: * @throws IOException
11: */
12: public static void main(String[] args) throws IOException{//建立檔案通常需要丟出 IOException 13: // TODO Auto-generated method stub
14:
15: /**建立目錄範例*/
16: File dir = new File("dirpath");//建立 file 物件(建立目錄用) 17: dir.mkdirs();//建立目錄(預設位置在專案路徑下)
18:
19: /**建立檔案範例*/
20: File file = new File("filepath","Test_IO.txt");//建立 file 物件(建立檔案用) 21: // file.createNewFile();//建立檔案 (執行錯誤,建立檔案若有指定目錄,必須先建立目錄再建立檔案
22: File filedir = new File("filepath");//先建立檔案的目錄的 file 物件 23: filedir.mkdirs();//建立檔案目錄
24: file.createNewFile();//建立檔案
25:
26: /**是否存在*/
27: if(dir.exists())
28: { 29: /**取得完整路徑*/
30: System.out.println(dir.getPath());// dirpath
31: }
32:
33: if(file.exists())
34: { 35: System.out.println(file.getPath());// file\Test_IO.txt
36: /**取得檔案大小*/
37: System.out.println(file.length());// 0
38: /**更改檔名*/
39: file.renameTo(new File(filedir,"Test_IO_2.txt"));
40:
41: //快速建立
42: new File(filedir,"Test_IO_3.txt").createNewFile();
43:
44: File tempfile = new File(filedir,"Test_IO_3.txt");
45: /**刪除檔案*/
46: tempfile.delete();
47: }
48: }
49:
50: }
想要存取檔案內容,必須先考慮檔案的格式,非文字檔使用 InputStream, OutputStream和其子類別,文字檔的話使用 Reader,Writer類別,如下
1: package Test_IO;
2:
3: import java.io.*;//使用檔案套件必須先import套件類別
4:
5: public class Test_IO_stream { 6:
7: /**
8: * @param args
9: */
10: public static void main(String[] args)throws IOException
11: { 12: // TODO Auto-generated method stub
13: /**FileOutputStream範例*/
14: FileOutputStream fos = new FileOutputStream("testfos.txt");//建立文字檔 15: String tempstr = "good java no use?好爪哇不用嗎";
16: fos.write(tempstr.getBytes());//寫入
17: fos.close();
18:
19:
20: /**FileInputStream範例*/
21: FileInputStream fis = new FileInputStream(new File("testfos.txt")); 22: for(int i2 =0; i2!=-1; i2 = fis.read())
23: { 24: System.out.print((char)i2);//good java no use??n???z??????
25: }
26: fis.close();
27:
28: System.out.println();
29:
30: /**FileWriter*/
31: FileWriter fw = new FileWriter("testwr.txt"); 32: String tempstr2 = "好爪哇不用嗎 good java no use";
33: fw.write(tempstr2);
34: fw.close();
35:
36:
37: FileReader fr = new FileReader("testwr.txt"); 38: for(int i=0; i!=-1;i = fr.read())
39: { 40: System.out.print((char)i);//好爪哇不用嗎 good java no use
41: }
42: }
43:
44: }
BufferedReader,BufferedWriter會在記憶體中製造緩衝區,等待資料充滿緩衝區後再一次處理,提高資料存取的效能,
1: package Test_IO;
2:
3: import java.io.*;
4:
5: public class Test_BufferedReader { 6:
7: /**
8: * @param args
9: */
10: public static void main(String[] args) throws IOException
11: { 12: // TODO Auto-generated method stub
13:
14: /**BufferedWriter , BufferedOutputStream範例*/
15: FileWriter fw = new FileWriter("testfw2.txt"); 16: FileOutputStream fos = new FileOutputStream("testfos2"); 17: //BufferedWriter bw = new BufferedWriter(fos); 錯誤 BufferedWriter 對應 FileWriter,不可使用在OutputStream上
18: BufferedWriter bw = new BufferedWriter(fw);//傳入參數為FileWriter
19: BufferedOutputStream bos = new BufferedOutputStream(fos);//傳入參數為FileOutputStream
20:
21: String temps1 = "好爪哇不用嗎";
22: String temps2 = "fweuhf3urhhf";
23:
24: //寫入
25: bw.write(temps1);
26: bw.close();
27: fw.close();
28:
29: //寫入
30: bos.write(temps2.getBytes());
31: bos.close();
32: fos.close();
33:
34: /**BufferedInputStream 範例*/
35: FileInputStream fis = new FileInputStream("testfos2"); 36: BufferedInputStream bis = new BufferedInputStream(fis);
37: int i = 0;
38: while((i = bis.read())!=-1)
39: { 40: System.out.print((char)i);
41: }
42: bis.close();
43: fis.close();
44:
45: System.out.println();
46:
47: /**BufferedReader 範例*/
48: FileReader fr = new FileReader("testfw2.txt"); 49: BufferedReader br = new BufferedReader(fr);
50: String stemp1 = "";
51: stemp1 = br.readLine();
52: System.out.println(stemp1);
br.close();
fr.close();
53: }
54:
55: }
也能把類別物件寫入檔案中,ObjectInputStream , ObjectOutputStream 可達到這個要求,必須注意要寫入檔案的類別必須實作 serializable 介面以序列化
1: package Test_IO;
2:
3: import java.io.*;
4:
5: public class Test_ObjectStream { 6:
7: /**
8: * @param args
9: */
10: public static void main(String[] args) throws Exception
11: { 12:
13: //ObjectOutputStream 範例
14: FileOutputStream fos = new FileOutputStream("testObject"); 15: ObjectOutputStream oos = new ObjectOutputStream(fos);
16:
17: for(int i =0; i<10; i++)
18: { 19: //寫入 object
20: oos.writeObject(new TestClass());
21: }
22:
23: oos.close();
24: fos.close();
25:
26:
27: ObjectInputStream ois = new ObjectInputStream(new FileInputStream("testObject")); 28:
29: //取出方法
30: while(1==1)
31: { 32: try{ 33:
34: ((TestClass)ois.readObject()).showtcNum();
35:
36: }
37: catch(EOFException eofe)
38: { 39: // eofe.printStackTrace();
40: }
41: }
42:
43:
44:
45: }
46:
47: }
48:
49: class TestClass implements Serializable //序列化 ,物件必須實作 serializable
50: { 51: int tcNum1;
52: String tcStr1;
53:
54: static int tcTotalCount;
55:
56: TestClass()
57: { 58: this.tcNum1 = tcTotalCount;
59: tcTotalCount++;
60: }
61:
62: public void showtcNum()
63: { 64: System.out.println(tcNum1);
65: }
66: }