设计模式 - Immutable 模式（Java不变集合类 vs Google Guava不变集合类）

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总结

JDK中的unmodifiableList的构造函数是对原始集合的浅拷贝，

而Guava.ImmutableList.copyOf是对原始集合的深拷贝

 

public class ImmutableDemo {
  public static void main(String[] args) {
    List<String> originalList = new ArrayList<>();
    originalList.add("a");
    originalList.add("b");
    originalList.add("c");

    List<String> jdkUnmodifiableList = Collections.unmodifiableList(originalList);
    List<String> guavaImmutableList = ImmutableList.copyOf(originalList);

    //jdkUnmodifiableList.add("d"); // 抛出UnsupportedOperationException
    // guavaImmutableList.add("d"); // 抛出UnsupportedOperationException
    originalList.add("d");

    print(originalList); // a b c d
    print(jdkUnmodifiableList); // a b c d  对原始list的修改，会影响java 不变集合类的结果
    print(guavaImmutableList); // a b c
  }

  private static void print(List<String> list) {
    for (String s : list) {
      System.out.print(s + " ");
    }
    System.out.println();
  }
}