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| 34. 20. 1. 使用访问者模式遍历文件系统 |
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import java.io.File;
public class VisitorTester {
public static void main(String[] args) {
DirectoryNode node = new DirectoryNode(new File(".."));
node.visit(new PrintVisitor());
}
}
class PrintVisitor {
int level = 0;
public void visitFileNode(FileNode node) {
for (int i = 0; i < level; i++)
System.out.print(" ");
System.out.println(node.getFile().getName());
}
public void visitDirectoryNode(DirectoryNode node) {
for (int i = 0; i < level; i++)
System.out.print(" ");
System.out.println(node.getDirectory().getName());
level++;
for (FileSystemNode c : node.getChildren())
c.visit(this);
level--;
}
}
interface FileSystemNode {
void visit(PrintVisitor v);
}
class FileNode implements FileSystemNode {
public FileNode(File file) {
this.file = file;
}
public File getFile() {
return file;
}
public void visit(PrintVisitor v) {
v.visitFileNode(this);
}
private File file;
}
class DirectoryNode implements FileSystemNode {
public DirectoryNode(File directory) {
this.directory = directory;
}
public void visit(PrintVisitor v) {
v.visitDirectoryNode(this);
}
public File getDirectory() {
return directory;
}
public FileSystemNode[] getChildren() {
File[] files = directory.listFiles();
FileSystemNode[] children = new FileSystemNode[files.length];
for (int i = 0; i < files.length; i++) {
File f = files[i];
if (f.isDirectory())
children[i] = new DirectoryNode(f);
else
children[i] = new FileNode(f);
}
return children;
}
private File directory;
}
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| 34. 20. 访问者模式 | | 34. 20. 1. | 使用访问者模式遍历文件系统 | | | | 34. 20. 2. | 访问模式，是一种多调度 | | |
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