《Java輸入輸出》的課堂示例代碼

《Java輸入輸出》的課堂小例子，針對輸入輸出流、字符流、字節流和文件操作等知識點

示例文件（共9個小例子，把相應注釋去掉後運行即可）

1. package com.lecheng;
3. import java.io.*;
5. public class MainTest {
7. /**
8. * @param args
9. */
10. public static void main(String[] args) {
11. //例子1 ：從一個文件讀數據，處理後存入另一個文件
12. /* try {
13. BufferedReader in = new BufferedReader(new FileReader("in.txt"));
14. PrintWriter out = new PrintWriter(new BufferedWriter(
15. new FileWriter("out.txt")));
16. String s;
17. int i = 1;
18. while ((s = in.readLine()) != null) {
19. out.println("line " + i + "=" + s);
20. i++;
21. }
22. in.close();
23. out.close();
24. System.out.println("完成！");
25. } catch (FileNotFoundException e) {
26. System.err.println("無法打開in.txt");
27. } catch (IOException e) {
28. System.err.println("I/O exception");
29. }*/
31. //例子2：用字符流方式從鍵盤讀入數據
32. // try{
33. // InputStreamReader isr= new InputStreamReader(System.in);
34. // BufferedReader is = new BufferedReader(isr);
35. // String inputLine;
36. // while((inputLine = is.readLine())!=null) {
37. // System.out.println(inputLine);
38. // }
39. // is.close();
40. // }catch(IOException e){
41. // System.out.println("IOException: " + e);
42. // }
44. //例子3：將各種數據類型的數據以字節流方式存入文件
45. // try{
46. // StudentPojo stu = new StudentPojo(1, "張三", "石家莊", 56.8, false);
47. // FileOutputStream fout = new FileOutputStream("text.txt");
48. // DataOutputStream out = new DataOutputStream(fout);
49. // out.writeInt(stu.getId());
50. // out.writeChar('\n');
51. // out.writeChars(stu.getName());
52. // out.writeChar('\n');
53. // out.writeChars(stu.getAddress());
54. // out.writeChar('\n');
55. // out.writeDouble(stu.getWeight());
56. // out.writeChar('\n');
57. // out.writeBoolean(stu.isSex());
58. //
59. // out.close();
60. // }catch(IOException e){
61. // }
62. //例子4：將例子3中的內容讀出
63. // DataInputStream in=null;
64. // try{
65. // in = new DataInputStream(new FileInputStream("text.txt"));
66. // int id;
67. // StringBuffer name, address;
68. // double weight;
69. // boolean sex;
70. // char ch;
71. // while(true){
72. // id = in.readInt();
73. // in.readChar();
74. // name = new StringBuffer(20);
75. // while((ch = in.readChar())!='\n'){
76. // name.append(ch);
77. // }
78. // address = new StringBuffer(20);
79. // while((ch = in.readChar())!='\n'){
80. // address.append(ch);
81. // }
82. // weight = in.readDouble();
83. // in.readChar();
84. // sex = in.readBoolean();
85. // System.out.println("ID:"+id);
86. // System.out.println("姓名:"+name);
87. // System.out.println("住址:"+address);
88. // System.out.println("體重:"+weight);
89. // System.out.println("性別:"+sex);
90. // }
91. // }catch(IOException e){
92. // }
93. //例子5：使用FileInputStream和FileOutputStream實現文件拷貝
94. /* try{
95. File inFile=new File("in.txt");
96. File outFile=new File("out.txt");
97. FileInputStream fis=new FileInputStream(inFile);
98. FileOutputStream fos=new FileOutputStream(outFile);
99. int i=0, c;
100. while((c=fis.read())!=-1){
101. fos.write(c);
102. }
103. fis.close();
104. fos.close();
105. }catch(FileNotFoundException e) {
106. System.err.println("FileStreamsTest: "+e);
107. }catch(IOException e) {
108. System.err.println("FileStreamsTest: "+e);
109. }*/
110. //例子6：獲取某路徑下文件信息
111. // File files = new File("c:\\");
112. // String fileList[] = files.list();
113. // for(int i = 0; i < fileList.length; i++){
114. // File currfiles = new File("c:\\"+fileList[i]);
115. // System.out.print("文件名：" + fileList[i] + "\t");
116. // System.out.println("文件大小：" + currfiles.length());
117. // }
118. //例子7：用字符流方式從鍵盤讀入數據後存入文件
119. // try{
120. // InputStreamReader isr= new InputStreamReader(System.in);
121. // BufferedReader br = new BufferedReader(isr);
122. // FileWriter fw = new FileWriter("char.txt");
123. // BufferedWriter bw = new BufferedWriter(fw);
124. // String str;
125. // while(true){
126. // System.out.print("請輸入一個字符串：");
127. // System.out.flush();
128. // str = br.readLine();
129. // if(str.length()==0){
130. // break;
131. // }
132. // bw.write(str);
133. // bw.newLine();
134. // }
135. // bw.close();
136. // }catch(IOException e){
137. // System.out.println("IOException: " + e);
138. // }
139. //例子8：用字符流方式從文件中讀入數據,用system.out輸出到屏幕
140. // try{
141. // FileReader fr = new FileReader("char.txt");
142. // BufferedReader br = new BufferedReader(fr);
143. // int lineNum = 0;
144. // String str = br.readLine();
145. // while(str != null){
146. // lineNum++;
147. // System.out.println("第"+lineNum+"行:"+str);
148. // str = br.readLine();
149. // }
150. // }catch(IOException e){
151. // System.out.println("IOException: " + e);
152. // }
153. //例子9：用字符流方式從文件中讀入數據,用流方式輸出到屏幕
154. // try{
155. // FileReader fr = new FileReader("char.txt");
156. // BufferedReader br = new BufferedReader(fr);
157. // OutputStreamWriter osw = new OutputStreamWriter(System.out);
158. // BufferedWriter bw = new BufferedWriter(osw);
159. // int lineNum = 0;
160. // String str = br.readLine();
161. //
162. // while(str != null){
163. // lineNum++;
164. // bw.write(String.valueOf(lineNum));
165. // bw.write(" ");
166. // bw.write(str);
167. // bw.newLine();
168. // str = br.readLine();
169. // }
170. // bw.close();
171. // }catch(IOException e){
172. // System.out.println("IOException: " + e);
173. // }
175. }
177. }

用到的POJO類

1. package com.lecheng;
3. public class StudentPojo {
4. private int id;
5. private String name;
6. private String address;
7. private double weight;
8. private boolean sex;
9. /**
10. * @param id
11. * @param name
12. * @param address
13. * @param weight
14. * @param sex
15. */
16. public StudentPojo(int id, String name, String address, double weight,
17. boolean sex) {
18. this.id = id;
19. this.name = name;
20. this.address = address;
21. this.weight = weight;
22. this.sex = sex;
23. }
24. /**
25. * @return the id
26. */
27. public int getId() {
28. return id;
29. }
30. /**
31. * @param id the id to set
32. */
33. public void setId(int id) {
34. this.id = id;
35. }
36. /**
37. * @return the name
38. */
39. public String getName() {
40. return name;
41. }
42. /**
43. * @param name the name to set
44. */
45. public void setName(String name) {
46. this.name = name;
47. }
48. /**
49. * @return the address
50. */
51. public String getAddress() {
52. return address;
53. }
54. /**
55. * @param address the address to set
56. */
57. public void setAddress(String address) {
58. this.address = address;
59. }
60. /**
61. * @return the weight
62. */
63. public double getWeight() {
64. return weight;
65. }
66. /**
67. * @param weight the weight to set
68. */
69. public void setWeight(double weight) {
70. this.weight = weight;
71. }
72. /**
73. * @return the sex
74. */
75. public boolean isSex() {
76. return sex;
77. }
78. /**
79. * @param sex the sex to set
80. */
81. public void setSex(boolean sex) {
82. this.sex = sex;
83. }
85. }