不可变类例子
//不可变类：类初始化后其属性不可改变，例如String、Double属于不可变类。//做法：1、把属性用private和final修饰 ；2、提供初始化属性的构造器；//3、只提供get方法不停工set方法public class Address {private final String detail;private final String postCode;public Address(String detail, String postCode) {super();this.detail = detail;this.postCode = postCode;}public Address() {this.detail ="";this.postCode="";}public String getDetail() {return detail;}public String getPostCode() {return postCode;}}

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