常用java代码
1 int 和 String 相互转换：
2 向文件中写入文本：
3 java代码截屏：
4 java创建zip和jar：
5 创建图片缩略图
6 发送http请求和提取数据
7 获取目录列表
8 Array 转 Map：
9 导出excel：http://blog.csdn.net/luqin1988/article/details/7680520
String a = String.valueOf(2);//integer to numeric string int i = Integer.parseInt(a);//numeric string to an int
2 向文件中写入文本：
BufferedWriter out = null;
try {
out = new BufferedWriter(new FileWriter("filename", true));
out.write("aString");
} catch (IOException e) {
// error processing code
} finally {
if (out != null) {
try {
out.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
3 java代码截屏：
import java.awt.Dimension;
import java.awt.Rectangle;
import java.awt.Robot;
import java.awt.Toolkit;
import java.awt.image.BufferedImage;
import java.io.File;
import javax.imageio.ImageIO;
/*******************************************************************
* 用Java实现屏幕截图
* 该JavaBean可以直接在其他Java应用程序中调用，实现屏幕的"拍照"
*****************************************************/
public class GuiCamera {
private String fileName; // 文件的前缀
private String defaultName = "GuiCamera";
static int serialNum = 0;
private String imageFormat; // 图像文件的格式
private String defaultImageFormat = "png";
Dimension d = Toolkit.getDefaultToolkit().getScreenSize();
/****************************************************************
* 默认的文件前缀为GuiCamera，文件格式为PNG格式 The default construct will use the default
* Image file surname "GuiCamera", and default image format "png"
****************************************************************/
public GuiCamera() {
fileName = defaultName;
imageFormat = defaultImageFormat;
}
/****************************************************************
* @param s
* the surname of the snapshot file
* @param format
* the format of the image file, it can be "jpg" or "png"
* 本构造支持JPG和PNG文件的存储
****************************************************************/
public GuiCamera(String s, String format) {
fileName = s;
imageFormat = format;
}
/****************************************************************
* 对屏幕进行拍照 snapShot the Gui once
****************************************************************/
public void snapShot() {
try {
// 拷贝屏幕到一个BufferedImage对象screenshot
BufferedImage screenshot = (new Robot())
.createScreenCapture(new Rectangle(0, 0,
(int) d.getWidth(), (int) d.getHeight()));
serialNum++;
// 根据文件前缀变量和文件格式变量，自动生成文件名
String name = fileName + String.valueOf(serialNum) + "."
+ imageFormat;
File f = new File(name);
System.out.print("Save File " + name);
// 将screenshot对象写入图像文件
ImageIO.write(screenshot, imageFormat, f);
System.out.print("..Finished!/n");
} catch (Exception ex) {
System.out.println(ex);
}
}
public static void main(String[] args) {
GuiCamera cam = new GuiCamera("d://Hello", "png");//
cam.snapShot();
}
}
4 java创建zip和jar：
import java.awt.Dimension;
import java.awt.Rectangle;
import java.awt.Robot;
import java.awt.Toolkit;
import java.awt.image.BufferedImage;
import java.io.File;
import javax.imageio.ImageIO;
/*******************************************************************
* 用Java实现屏幕截图
* 该JavaBean可以直接在其他Java应用程序中调用，实现屏幕的"拍照"
*****************************************************/
public class GuiCamera {
private String fileName; // 文件的前缀
private String defaultName = "GuiCamera";
static int serialNum = 0;
private String imageFormat; // 图像文件的格式
private String defaultImageFormat = "png";
Dimension d = Toolkit.getDefaultToolkit().getScreenSize();
/****************************************************************
* 默认的文件前缀为GuiCamera，文件格式为PNG格式 The default construct will use the default
* Image file surname "GuiCamera", and default image format "png"
****************************************************************/
public GuiCamera() {
fileName = defaultName;
imageFormat = defaultImageFormat;
}
/****************************************************************
* @param s
* the surname of the snapshot file
* @param format
* the format of the image file, it can be "jpg" or "png"
* 本构造支持JPG和PNG文件的存储
****************************************************************/
public GuiCamera(String s, String format) {
fileName = s;
imageFormat = format;
}
/****************************************************************
* 对屏幕进行拍照 snapShot the Gui once
****************************************************************/
public void snapShot() {
try {
// 拷贝屏幕到一个BufferedImage对象screenshot
BufferedImage screenshot = (new Robot())
.createScreenCapture(new Rectangle(0, 0,
(int) d.getWidth(), (int) d.getHeight()));
serialNum++;
// 根据文件前缀变量和文件格式变量，自动生成文件名
String name = fileName + String.valueOf(serialNum) + "."
+ imageFormat;
File f = new File(name);
System.out.print("Save File " + name);
// 将screenshot对象写入图像文件
ImageIO.write(screenshot, imageFormat, f);
System.out.print("..Finished!/n");
} catch (Exception ex) {
System.out.println(ex);
}
}
public static void main(String[] args) {
GuiCamera cam = new GuiCamera("d://Hello", "png");//
cam.snapShot();
}
}
5 创建图片缩略图
public void createThumbnail(String filename, int thumbWidth,
int thumbHeight, int quality, String outFilename)
throws InterruptedException, FileNotFoundException, IOException {
// load image from filename
Image image = Toolkit.getDefaultToolkit().getImage(filename);
MediaTracker mediaTracker = new MediaTracker(new Container());
mediaTracker.addImage(image, 0);
mediaTracker.waitForID(0);
// use this to test for errors at this point:
// System.out.println(mediaTracker.isErrorAny());
// determine thumbnail size from WIDTH and HEIGHT
double thumbRatio = (double) thumbWidth / (double) thumbHeight;
int imageWidth = image.getWidth(null);
int imageHeight = image.getHeight(null);
double imageRatio = (double) imageWidth / (double) imageHeight;
if (thumbRatio < imageRatio) {
thumbHeight = (int) (thumbWidth / imageRatio);
} else {
thumbWidth = (int) (thumbHeight * imageRatio);
}
// draw original image to thumbnail image object and
// scale it to the new size on-the-fly
BufferedImage thumbImage = new BufferedImage(thumbWidth, thumbHeight,
BufferedImage.TYPE_INT_RGB);
Graphics2D graphics2D = thumbImage.createGraphics();
graphics2D.setRenderingHint(RenderingHints.KEY_INTERPOLATION,
RenderingHints.VALUE_INTERPOLATION_BILINEAR);
graphics2D.drawImage(image, 0, 0, thumbWidth, thumbHeight, null);
// save thumbnail image to outFilename
BufferedOutputStream out = new BufferedOutputStream(
new FileOutputStream(outFilename));
JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
JPEGEncodeParam param = encoder.getDefaultJPEGEncodeParam(thumbImage);
quality = Math.max(0, Math.min(quality, 100));
param.setQuality((float) quality / 100.0f, false);
encoder.setJPEGEncodeParam(param);
encoder.encode(thumbImage);
out.close();
}
6 发送http请求和提取数据
try {
URL my_url = new URL("www.baidu.com/");
BufferedReader br = new BufferedReader(new InputStreamReader(my_url
.openStream()));
String strTemp = "";
while (null != (strTemp = br.readLine())) {
System.out.println(strTemp);
}
} catch (Exception ex) {
ex.printStackTrace();
}
7 获取目录列表
File dir = new File("directoryName");
String[] children = dir.list();
if (children == null) {
// Either dir does not exist or is not a directory
} else {
for (int i = 0; i < children.length; i++)
{
// Get filename of file or directory
String filename = children[i];
}
}
// It is also possible to filter the list of returned files.
// This example does not return any files that start with `.'.
FilenameFilter filter = new FilenameFilter() {
public boolean accept(File dir, String name) {
return !name.startsWith(".");
}
};
children = dir.list(filter);
// The list of files can also be retrieved as File objects
File[] files = dir.listFiles();
// This filter only returns directories
FileFilter fileFilter = new FileFilter() {
public boolean accept(File file) {
return file.isDirectory();
}
};
files = dir.listFiles(fileFilter);
8 Array 转 Map：
String[][] countries = { { "United States", "New York" },
{ "United Kingdom", "London" }, { "Netherland", "Amsterdam" },
{ "Japan", "Tokyo" }, { "France", "Paris" } };
Map countryCapitals = ArrayUtils.toMap(countries);
System.out.println("Capital of Japan is "
+ countryCapitals.get("Japan"));
System.out.println("Capital of France is "
+ countryCapitals.get("France"));
9 导出excel：http://blog.csdn.net/luqin1988/article/details/7680520