Java在转换为对象后更改变量的值

Question

我试图在将变量转换为对象后更改它。这在 Java 中可能吗？或者还有其他选项可以做类似的事情吗？

Double a = 1.;
Object o = a;
Double b = (Double)o;
b = 2.;
System.out.println(a); // print 2

Answer 1

如果有两个引用指向同一个对象，则无法更改这两个引用，将其分配给一个新对象。

Double a = 1.,
Double b = a;
Double b = 2.; // here b now points to new object. a is not changed. Now you have two separate variables pointing to separate objects.

如果你真的需要它，那么你需要使用具有setter/better的包装类来操纵内部状态

DoubleWrapper a = new DoubleWrapper(2); // not a standard JDK class. You will need to write it yourself
DoubleWrapper b = a;
b.set(1);
System.out.println(b.get()); // prints 1
System.out.println(a.get()); // also prints 1