如何在 Java 中复制对象? [英] How do I copy an object in Java?

问题描述

考虑下面的代码:

DummyBean dum = new DummyBean();
dum.setDummy("foo");
System.out.println(dum.getDummy()); // prints 'foo'

DummyBean dumtwo = dum;
System.out.println(dumtwo.getDummy()); // prints 'foo'

dum.setDummy("bar");
System.out.println(dumtwo.getDummy()); // prints 'bar' but it should print 'foo'

所以，我想将 dum 复制到 dumtwo 并更改 dum 而不影响 dumtwo.但是上面的代码并没有这样做.当我在 dum 中更改某些内容时，dumtwo 中也会发生相同的更改.

So, I want to copy the dum to dumtwo and change dum without affecting the dumtwo. But the code above is not doing that. When I change something in dum, the same change is happening in dumtwo also.

我想，当我说 dumtwo = dum 时，Java 会复制仅引用.那么，有没有办法创建一个 dum 的新副本并将其分配给 dumtwo?

I guess, when I say dumtwo = dum, Java copies the reference only. So, is there any way to create a fresh copy of dum and assign it to dumtwo?

推荐答案

创建复制构造函数:

class DummyBean {
  private String dummy;

  public DummyBean(DummyBean another) {
    this.dummy = another.dummy; // you can access  
  }
}

每个对象都有一个克隆方法，可以用来复制对象，但不要使用它.创建一个类并执行不正确的克隆方法太容易了.如果您打算这样做，请至少阅读 Joshua Bloch 在有效的 Java.

Every object has also a clone method which can be used to copy the object, but don't use it. It's way too easy to create a class and do improper clone method. If you are going to do that, read at least what Joshua Bloch has to say about it in Effective Java.

这篇关于如何在 Java 中复制对象?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！