forindemo.java

来自「Java5.0 Tiger 程序员高手秘笈一书的源代码」· Java 代码 · 共 47 行

package com.oreilly.tiger.ch07;

import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

public class ForInDemo {

  public static void main(String[] args) {

    // These are collections we抣l iterate over below.
    List wordlist = new ArrayList();
    Set wordset = new HashSet();

    // We start with a basic loop over the elements of an array.
    // The body of the loop is executed once for each element of args[].
    // Each time through one element is assigned to the variable word.
    System.out.println("Assigning arguments to lists...");
    for(String word : args) {
      System.out.print(word + " ");
      wordlist.add(word);
      wordset.add(word);
    }

    System.out.println();

    // Iterate through the elements of the List now.
    // Since lists have an order, these words should appear as above
    System.out.println("Printing words from wordlist " +
      "(ordered, with duplicates)...");
    for(Object word : wordlist) {
      System.out.print((String)word + " ");
    }

    System.out.println();

    // Do the same for the Set. The loop looks the same but by virtue of
    // using a Set, we lose the word order and also discard duplicates.
    System.out.println("Printing words from wordset " +
      "(unordered, no duplicates)...");
    for(Object word : wordset) {
      System.out.print((String)word + " ");
    }
  }
}