如何import外部Jar文件中位于default package下的classes

本文介绍了在Java中如何处理无法直接import默认包下类的问题。通过使用jarjar工具,可以将默认包的类重新打包到指定的包名下,从而避免编译错误。具体操作包括创建rule.txt文件定义规则,并使用java -jar jarjar.jar process命令执行repackage过程。

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目前Java已经禁止import未命名package下的class:
From the Java language spec:  It is a compile time error to import a type from the unnamed package.

package com.test; import java.awt.image.BufferedImage; import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.IOException; public class B { public static void main(String[] args) { File file = new File("c:\\a.jpg"); FileInputStream is = null; try { is = new FileInputStream(file); } catch (FileNotFoundException e2) { e2.printStackTrace(); // return rect; } BufferedImage sourceImg = null; try { sourceImg = javax.imageio.ImageIO.read(is); } catch (IOException e1) { e1.printStackTrace(); // return rect; } System.out.println("width = " + sourceImg.getWidth() + "height = " + sourceImg.getHeight()); } } package com.test; import java.awt.image.BufferedImage; import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.IOException; public class B { public static void main(String[] args) { File file = new File("c:\\a.jpg"); FileInputStream is = null; try { is = new FileInputStream(file); } catch (FileNotFoundException e2) { e2.printStackTrace(); // return rect; } BufferedImage sourceImg = null; try { sourceImg = javax.imageio.ImageIO.read(is); } catch (IOException e1) { e1.printStackTrace(); // return rect; } System.out.println("width = " + sourceImg.getWidth() + "height = " + sourceImg.getHeight()); } } package com.test; import java.awt.image.BufferedImage; import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.IOException; public class B { public static void main(String[] args) { File file = new File("c:\\a.jpg"); FileInputStream is = null; try { is = new FileInputStream(file); } catch (FileNotFoundException e2) { e2.printStackTrace(); // return rect; } BufferedImage sourceImg = null; try { sourceImg = javax.imageio.ImageIO.read(is); } catch (IOException e1) { e1.printStackTrace(); // return rect; } System.out.println("width = " + sourceImg.getWidth() + "height = " + sourceImg.getHeight()); } } package com.test; import java.awt.image.BufferedImage; import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.IOException; public class B { public static void main(String[] args) { File file = new File("c:\\a.jpg"); FileInputStream is = null; try { is = new FileInputStream(file); } catch (FileNotFoundException e2) { e2.printStackTrace(); // return rect; } BufferedImage sourceImg = null; try { sourceImg = javax.imageio.ImageIO.read(is); } catch (IOException e1) { e1.printStackTrace(); // return rect; } System.out.println("width = " + sourceImg.getWidth() + "height = " + sourceImg.getHeight()); } }
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