Go语言视频零基础入门到精通

五菱

1. 把Strings转换成int和把int转换成String

2. String a = String.valueOf(2);
3.             //integer to numeric string   
4.             int i = Integer.parseInt(a); //numeric
5.             string to an int
6.             
7.             String a = String.valueOf(2);   
8.             //integer to numeric string
9.             int i = Integer.parseInt(a); //numeric string to an int

复制代码

2. 向java文件中添加文本

2. java.util.Date =
3.             java.text.DateFormat.getDateInstance().parse(date String);
4.             
5.             java.util.Date = java.text.DateFormat.getDateInstance().parse(date
6.             String);or
7.             SimpleDateFormat format = new SimpleDateFormat( "dd.MM.yyyy"
8.             );   
9.             Date date = format.parse( myString );
10.             SimpleDateFormat format = new SimpleDateFormat( "dd.MM.yyyy" );
11.             Date date
12.             = format.parse( myString );
14. Updated: Thanks Simone for pointing to exception. I havechanged the code.
15. BufferedWriter ut = null;   
16. try{   
17. out = new BufferedWriter(new FileWriter(”filename”, true));   
18. out.write(”aString”);   
19. } catch (IOException e) {   
20. // error processing code   
21. } finally{   
22. if (out != null) {   
23. out.close();   
24. }   
25. }   
27. BufferedWriter ut = null;
28. try {
29. out = new BufferedWriter(newFileWriter(”filename”, true));
30. out.write(”aString”);
31. } catch(IOException e) {
32. // error processing code
33. } finally {
34. if (out!= null) {
35. out.close();
36. }
37. }

复制代码

3. 获取java现在正调用的方法名

2. String methodName =
3.             Thread.currentThread().getStackTrace()[1].getMethodName();
4.             String methodName = Thread.currentThread().getStackTrace()[1].getMethodName
5.             ();

复制代码

4. 在java中将String型转换成Date型

2. java.util.Date =
3.             java.text.DateFormat.getDateInstance().parse(date String);
4.             
5.             java.util.Date = java.text.DateFormat.getDateInstance().parse(date
6.             String);or
7.             SimpleDateFormat format = new SimpleDateFormat( "dd.MM.yyyy"
8.             );   
9.             Date date = format.parse( myString );
10.             SimpleDateFormat format = new SimpleDateFormat( "dd.MM.yyyy" );
11.             Date date
12.             = format.parse( myString );

复制代码

5. 通过java jdbc链接oracle数据库

2. public class oraclejdbcTest   
3. {   
4. String driverClass =
5. "oracle.jdbc.driver.oracleDriver";   
6. Connection con;   
7. public void init
8. (FileInputStream fs) throws ClassNotFoundException,
10. SQLException, FileNotFoundException, IOException   
11. {   
12. Properties props = new Properties();   
13. props.load(fs);   
14. String url = props.getProperty
15. ("db.url");   
16. String
17. userName = props.getProperty("db.user");   
18. String password = props.getProperty
19. ("db.password");   
20. Class.forName(driverClass);   
21. con=DriverManager.getConnection(url,
22. userName, password);   
23. }   
24. public void fetch() throws SQLException,
25. IOException   
26. {   
27. PreparedStatement ps =
28. con.prepareStatement("select SYSDATE from dual");   
29. ResultSet rs = ps.executeQuery
30. ();   
31. while
32. (rs.next())   
33. {   
34. // do the
35. thing you do   
36. }
37.    
38. rs.close();   
39. ps.close();   
40. }   
41. public
42. static void main(String[] args)   
43. {   
44. oraclejdbcTest test = new
45. oraclejdbcTest();   
46. test.init();   
47. test.fetch
48. ();   
49. }   
50. }
51. public class oraclejdbcTest
52. {
53. String driverClass =
54. "oracle.jdbc.driver.oracleDriver";
55. Connection con;
56. public void init(FileInputStream fs) throws ClassNotFoundException,
57. SQLException, FileNotFoundException, IOException
58. {
59. Properties props = new Properties();
60. props.load
61. (fs);
62. String url = props.getProperty
63. ("db.url");
64. String userName = props.getProperty
65. ("db.user");
66. String password = props.getProperty
67. ("db.password");
68. Class.forName(driverClass);
69. con=DriverManager.getConnection(url, userName,
70. password);
71. }
72. public void fetch() throws SQLException, IOException
73. {
74. PreparedStatement ps = con.prepareStatement("select SYSDATE from
75. dual");
76. ResultSet rs = ps.executeQuery();
77. while (rs.next())
78. {
79. // do the
80. thing you do
81. }
82. rs.close();
83. ps.close
84. ();
85. }
86. public static void main(String[] args)
87. {
88. oraclejdbcTest test = new oraclejdbcTest
89. ();
90. test.init();
91. test.fetch();
92. }
93. }

复制代码

6.将java中的util.Date转换成sql.Date
这一片段显示如何将一个java util Date转换成sql Date用于数据库

2. java.util.Date utilDate = new
3.             java.util.Date();   
4.             java.sql.Date sqlDate = new java.sql.Date
5.             (utilDate.getTime());
6.             
7.             java.util.Date utilDate = new java.util.Date();
8.             java.sql.Date sqlDate =
9.             new java.sql.Date(utilDate.getTime());

复制代码

7. 使用NIO快速复制java文件

3. public static void fileCopy( File in, File out )
4.    
5. throws IOException   
6. {   
7. FileChannel inChannel = new
8. FileInputStream( in ).getChannel();   
9. FileChannel utChannel = new
10. FileOutputStream( out ).getChannel();   
11. try
12. {   
13. //          inChannel.transferTo
14. (0, inChannel.size(), outChannel);      // original
16. -- apparently has trouble copying large files on Windows   
17. // magic
18. number for Windows, 64Mb - 32Kb)   
19. int maxCount
20. = (64 * 1024 * 1024) - (32 * 1024);   
21. long size =
22. inChannel.size();   
23. long
24. position = 0;   
25. while (
26. position < size )   
27. {   
28. &
29. nbsp; position += inChannel.transferTo( position, maxCount, outChannel );
30. }
31.    
32. }   
33. finally
34. {   
35. if (
36. inChannel != null )   
37. {   
38. &
39. nbsp; inChannel.close();   
40. }
41.    
42. if ( outChannel != null )   
43. {   
44. &
45. nbsp;  outChannel.close();   
46. }
47.    
48. }   
49. }
50. public static void fileCopy( File in, File out )
51. throws
52. IOException
53. {
54. FileChannel inChannel = new FileInputStream( in ).getChannel
55. ();
56. FileChannel utChannel = new
57. FileOutputStream( out ).getChannel();
58. try
59. {
60. //          inChannel.transferTo
61. (0, inChannel.size(), outChannel);      // original
62. -- apparently has trouble copying large files on Windows
63. // magic
64. number for Windows, 64Mb - 32Kb)
65. int maxCount
66. = (64 * 1024 * 1024) - (32 *
67. 1024);
68. long
69. size = inChannel.size
70. ();
71. long
72. position = 0;
73. while ( position < size )
74. {
75.   position += inChannel.transferTo( position, maxCount, outChannel
76. );
77. }
78. }
79. finally
80. {
81. if (
82. inChannel != null )
83. {
84.   inChannel.close
85. ();
86. }
87. if (
88. outChannel != null )
89. {
90.    outChannel.close
91. ();
92. }
93. }
94. }

复制代码

8. 在java中创建缩略图

2. private void createThumbnail(String filename, int thumbWidth,
3. int thumbHeight, int
5. quality, String outFilename)   
6. throws InterruptedException,
7. FileNotFoundException, IOException   
8. {   
9. // load image from
10. filename   
11. Image image =
12. Toolkit.getDefaultToolkit().getImage(filename);   
13. MediaTracker mediaTracker = new
14. MediaTracker(new Container());   
15. mediaTracker.addImage(image,
16. 0);   
17. mediaTracker.waitForID(0);   
18. // use this to test for errors at
19. this point: System.out.println
20. (mediaTracker.isErrorAny());   
21. // determine thumbnail size from
22. WIDTH and HEIGHT   
23. double
24. thumbRatio = (double)thumbWidth / (double)thumbHeight;   
25. int imageWidth = image.getWidth
26. (null);   
27. int imageHeight
28. = image.getHeight(null);   
29. double imageRatio = (double)imageWidth / (double)imageHeight;   
30. if (thumbRatio < imageRatio)
31. {   
32. thumbHeight
33. = (int)(thumbWidth / imageRatio);   
34. } else {   
35. thumbWidth =
36. (int)(thumbHeight * imageRatio);   
37. }   
38. // draw original image to thumbnail
39. image object and   
40. //
41. scale it to the new size on-the-fly   
42. BufferedImage thumbImage = new
43. BufferedImage(thumbWidth, thumbHeight,
44. BufferedImage.TYPE_INT_RGB);   
45. Graphics2D graphics2D =
46. thumbImage.createGraphics();   
47. graphics2D.setRenderingHint
48. (RenderingHints.KEY_INTERPOLATION,
49. RenderingHints.VALUE_INTERPOLATION_BILINEAR);   
50. graphics2D.drawImage(image, 0, 0,
51. thumbWidth, thumbHeight, null);   
52. // save thumbnail image to
53. outFilename   
54. BufferedOutputStream ut = new BufferedOutputStream(new FileOutputStream
55. (outFilename));   
56. JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);   
57. JPEGEncodeParam param =
58. encoder.getDefaultJPEGEncodeParam(thumbImage);   
59. quality = Math.max(0, Math.min
60. (quality, 100));   
61. param.setQuality((float)quality / 100.0f, false);   
62. encoder.setJPEGEncodeParam
63. (param);   
64. encoder.encode
65. (thumbImage);   
66. out.close
67. ();   
68. }
69. private void createThumbnail(String filename, int thumbWidth, int
70. thumbHeight, int
71. quality, String outFilename)
72. throws InterruptedException,
73. FileNotFoundException, IOException
74. {
75. // load image from
76. filename
77. Image image = Toolkit.getDefaultToolkit().getImage
78. (filename);
79. MediaTracker mediaTracker = new MediaTracker(new
80. Container());
81. mediaTracker.addImage(image,
82. 0);
83. mediaTracker.waitForID(0);
84. // use this to test
85. for errors at this point: System.out.println
86. (mediaTracker.isErrorAny());
87. // determine thumbnail size from WIDTH and
88. HEIGHT
89. double thumbRatio = (double)thumbWidth / (double)
90. thumbHeight;
91. int imageWidth = image.getWidth
92. (null);
93. int imageHeight = image.getHeight
94. (null);
95. double imageRatio = (double)imageWidth / (double)
96. imageHeight;
97. if (thumbRatio < imageRatio)
98. {
99. thumbHeight = (int)(thumbWidth /
100. imageRatio);
101. } else {
102. thumbWidth = (int)
103. (thumbHeight * imageRatio);
104. }
105. // draw original image to thumbnail image object
106. and
107. // scale it to the new size on-the-
108. fly
109. BufferedImage thumbImage = new BufferedImage(thumbWidth,
110. thumbHeight, BufferedImage.TYPE_INT_RGB);
111. Graphics2D graphics2D =
112. thumbImage.createGraphics();
113. graphics2D.setRenderingHint
114. (RenderingHints.KEY_INTERPOLATION,
115. RenderingHints.VALUE_INTERPOLATION_BILINEAR);
116. graphics2D.drawImag
117. e(image, 0, 0, thumbWidth, thumbHeight, null);
118. // save thumbnail image to
119. outFilename
120. BufferedOutputStream ut = new BufferedOutputStream(new
121. FileOutputStream(outFilename));
122. JPEGImageEncoder encoder =
123. JPEGCodec.createJPEGEncoder(out);
124. JPEGEncodeParam param =
125. encoder.getDefaultJPEGEncodeParam
126. (thumbImage);
127. quality = Math.max(0, Math.min(quality,
128. 100));
129. param.setQuality((float)quality / 100.0f,
130. false);
131. encoder.setJPEGEncodeParam
132. (param);
133. encoder.encode(thumbImage);
134. out.close
135. ();
136. }

复制代码

9. 在java中创建JSON数据

2. Read this article for more details.
3. Download JAR file json
4. -rpc-1.0.jar (75 kb)
7. import org.json.JSONObject;   
8. ...   
9. ...   
10. JSONObject json = new JSONObject();   
11. json.put("city", "Mumbai");   
12. json.put("country",
13. "India");   
14. ...   
15. String utput = json.toString
16. ();   
17. ...
18. import org.json.JSONObject;
19. ...
20. ...
21. JSONObject json = new
22. JSONObject();
23. json.put("city", "Mumbai");
24. json.put("country",
25. "India");
26. ...
27. String utput = json.toString();
28. ...

复制代码

10. 在java中使用iText JAR打开PDF

2. Read this article for more details.
5. import java.io.File;   
6. import
7. java.io.FileOutputStream;   
8. import java.io.OutputStream;   
9. import java.util.Date;   
10. import
11. com.lowagie.text.Document;   
12. import
13. com.lowagie.text.Paragraph;   
14. import
15. com.lowagie.text.pdf.PdfWriter;   
16. public class GeneratePDF
17. {   
18. public static void main(String[]
19. args) {   
20. try
21. {   
22. OutputStream
23. file = new FileOutputStream(new File("C:\\Test.pdf"));   
24. Document
25. document = new Document();   
26. PdfWriter.getInstance(document, file);   
27. document.open();   
28. document.add(new Paragraph("Hello Kiran"));   
29. document.add(new Paragraph(new Date().toString()));   
30. document.close();   
31. file.close
32. ();   
33. } catch
34. (Exception e) {   
35. e.printStackTrace();   
36. }
37.    
38. }   
39. }
40. import java.io.File;
41. import java.io.FileOutputStream;
42. import
43. java.io.OutputStream;
44. import java.util.Date;
45. import com.lowagie.text.Document;
46. import
47. com.lowagie.text.Paragraph;
48. import com.lowagie.text.pdf.PdfWriter;
49. public class GeneratePDF {
50. public static void main(String[] args)
51. {
52. try
53. {
54. OutputStream file = new FileOutputStream(new File("C:\\Test.pdf"));
55. Document
56. document = new Document
57. ();
58. PdfWriter.getInstance(document,
59. file);
60. document.open
61. ();
62. document.add(new Paragraph("Hello
63. Kiran"));
64. document.add(new Paragraph(new Date().toString()));
65. document.close
66. ();
67. file.close();
68. } catch (Exception e) {
69. e.printStackTrace();
70. }
71. }
72. }

复制代码

gnwe1990

谢谢楼主分享。