files - Adding and Subtracting Paths

最新推荐文章于 2023-08-30 16:17:39 发布

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本文深入探讨了Java中Path对象的创建、添加与减法操作，通过具体实例展示了如何使用relativize()和resolve()方法来处理文件路径。文章涵盖了路径规范化、绝对路径转换及解决复杂路径表达式等内容。

We must be able to construct Path objects by adding and subtracting pieces to our Path. To subtract the base of a Path we use relativize() and to add pieces at the end of a Path we use resolve() (not exactly “discoverable” names).

// files/AddAndSubtractPaths.java
// (c)2017 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://OnJava8.com for more book information.

import java.io.IOException;
import java.nio.file.*;

public class AddAndSubtractPaths {
  static Path base = Paths.get("..", "..", "..").toAbsolutePath().normalize();

  static void show(int id, Path result) {
    if (result.isAbsolute()) {
      System.out.println("(" + id + ") " + base.relativize(result));
    } else {
      System.out.println("(" + id + ")  " + result);
    }
    try {
      System.out.println("RealPath: " + result.toRealPath());
    } catch (IOException e) {
      System.out.println(e);
    }
  }

  public static void main(String[] args) {
    System.out.println(System.getProperty("os.name"));
    System.out.println(base);
    Path p = Paths.get("AddAndSubtractPaths.java").toAbsolutePath();
    show(1, p);
    Path convoluted =
        p.getParent()
            .getParent()
            .resolve("strings")
            .resolve("..")
            .resolve(p.getParent().getFileName());
    System.out.println(
        "convoluted ..:" + p.getParent().getParent().resolve("strings").resolve(".."));
    show(2, convoluted);
    show(3, convoluted.normalize());

    Path p2 = Paths.get("..", "..");
    show(4, p2);
    show(5, p2.normalize());
    show(6, p2.toAbsolutePath().normalize());

    Path p3 = Paths.get(".").toAbsolutePath();
    Path p4 = p3.resolve(p2);
    show(7, p4);
    show(8, p4.normalize());

    Path p5 = Paths.get("").toAbsolutePath();
    show(9, p5);
    show(10, p5.resolveSibling("strings"));
    show(11, Paths.get("nonexistent"));
  }
}
/* My Output:
Mac OS X
/Users/wangbingfeng
(1) github/OnJava8-Examples/files/AddAndSubtractPaths.java
RealPath: /Users/wangbingfeng/github/OnJava8-Examples/files/AddAndSubtractPaths.java
convoluted:/Users/wangbingfeng/github/OnJava8-Examples/strings
convoluted ..:/Users/wangbingfeng/github/OnJava8-Examples/strings/..
(2) github/OnJava8-Examples/strings/../files
RealPath: /Users/wangbingfeng/github/OnJava8-Examples/files
(3) github/OnJava8-Examples/files
RealPath: /Users/wangbingfeng/github/OnJava8-Examples/files
(4)  ../..
RealPath: /Users/wangbingfeng/github

(5)  ../..
RealPath: /Users/wangbingfeng/github
(6) github
RealPath: /Users/wangbingfeng/github
(7) github/OnJava8-Examples/files/./../..
RealPath: /Users/wangbingfeng/github
(8) github
RealPath: /Users/wangbingfeng/github
(9) github/OnJava8-Examples/files
RealPath: /Users/wangbingfeng/github/OnJava8-Examples/files
(10) github/OnJava8-Examples/strings
RealPath: /Users/wangbingfeng/github/OnJava8-Examples/strings
(11)  nonexistent
java.nio.file.NoSuchFileException: nonexistent
*/

resolve

Path resolve(String other)

Converts a given path string to a Path and resolves it against this Path in exactly the manner specified by the resolve method. For example, suppose that the name separator is "/" and a path represents "foo/bar", then invoking this method with the path string "gus" will result in the Path "foo/bar/gus".

Parameters:

other - the path string to resolve against this path

Returns:

the resulting path

Throws:

InvalidPathException - if the path string cannot be converted to a Path.