也许像
class A { String a; List<..> b; int c; public void merge(A other) { this.a = other.a == null ? this.a : other.a; this.b.addAll(other.b); this.c = other.c == 0 ? this.c : other.c; }}A a1 = new A();A a2 = new A();a1.a = "a prop";a2.c = 34;a1.merge(a2);A.merge可能会返回一个新
A对象，而不是修改当前对象。
