java-think in java 检测工程索引列表

java--think in java 检测工程目录列表

think in java 第四版第18.1.1章节，列出了3套代码，来表示一个功能的三种实现。

三种不同的实现，对代码进行了不同程度压缩。

代码：

package io;

//: io/DirList.java
// Display a directory listing using regular expressions.
// {Args: "D.*\.java"}
import java.util.regex.*;
import java.io.*;
import java.util.*;

public class DirList {
  public static void main(String[] args) {
    File path = new File(".");
    String[] list;
    if(args.length == 0)
      list = path.list();
    else
      list = path.list(new DirFilter(args[0]));
    Arrays.sort(list, String.CASE_INSENSITIVE_ORDER);
    for(String dirItem : list)
      System.out.println(dirItem);
  }
}

class DirFilter implements FilenameFilter {
  private Pattern pattern;
  public DirFilter(String regex) {
    pattern = Pattern.compile(regex);
  }
  public boolean accept(File dir, String name) {
    return pattern.matcher(name).matches();
  }
} /* Output:
DirectoryDemo.java
DirList.java
DirList2.java
DirList3.java
*///:~

package io;

//: io/DirList2.java
// Uses anonymous inner classes.
// {Args: "D.*\.java"}
import java.util.regex.*;
import java.io.*;
import java.util.*;

public class DirList2 {
  public static FilenameFilter filter(final String regex) {
    // Creation of anonymous inner class:
    return new FilenameFilter() {
      private Pattern pattern = Pattern.compile(regex);
      public boolean accept(File dir, String name) {
        return pattern.matcher(name).matches();
      }
    }; // End of anonymous inner class
  }
  public static void main(String[] args) {
    File path = new File(".");
    String[] list;
    if(args.length == 0)
      list = path.list();
    else
      list = path.list(filter(args[0]));
    Arrays.sort(list, String.CASE_INSENSITIVE_ORDER);
    for(String dirItem : list)
      System.out.println(dirItem);
  }
} /* Output:
DirectoryDemo.java
DirList.java
DirList2.java
DirList3.java
*///:~

在list方法使用匿名内部类作为方法的参数。

优点：代码隔离、聚拢于一点。

缺点：不易阅读。

package io;

//: io/DirList3.java
// Building the anonymous inner class "in-place."
// {Args: "D.*\.java"}
import java.util.regex.*;
import java.io.*;
import java.util.*;

public class DirList3 {
  public static void main(final String[] args) {
    File path = new File(".");
    String[] list;
    if(args.length == 0)
      list = path.list();
    else
      list = path.list(new FilenameFilter() {
        private Pattern pattern = Pattern.compile(args[0]);
        public boolean accept(File dir, String name) {
          return pattern.matcher(name).matches();
        }
      });
    Arrays.sort(list, String.CASE_INSENSITIVE_ORDER);
    for(String dirItem : list)
      System.out.println(dirItem);
  }
} /* Output:
DirectoryDemo.java
DirList.java
DirList2.java
DirList3.java
*///:~

java-think in java 检测工程索引列表

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