如何从对象数组中获取对象，基于对象字段[复制]

Question

我有个简单的课

class Employee {
    private String id;
    private String name;
    private String address;

    Employee(String id) {
        this.id = id;
    }
}

我创建了这个类的样本对象的ArrayList

List<Employee> employees = new ArrayList<>();

employees.add(new Employee("101"));
employees.add(new Employee("106"));
employees.add(new Employee("108"));

这里没有显示我后来如何填充对象的其他字段（名称，地址等）

有没有一种方法可以使用字母数字字符串id快速检索其中一个对象，而无需遍历整个列表？（没有实现数据库层）

差不多

employees.getById("101");

Answer 1

//ArrayList of Employees:
List<Employee> employees = new ArrayList<>();
employees.add(new Employee("101". "Name101", "Address101"));


//As of Java 8, to find an element matching specific criteria in list:
Employee getById("101"); // return Employee with id "101"

private Employee getById(String id) {
   return employees.stream()  // invoke stream() on the list
    .filter(employee-> id.equals(employee.getId()))  //  method with a proper predicate
    .findAny() // which returns the first element that matches the filter predicate wrapped in an Optional if such an element exists
    .orElse(null); // return null if not exist
}

Answer 2

你可以用一张地图

将对象放入地图

Map<String,Employee> employees = new HashMap<>();

// employees.put({key},{object});
employees.put("101",new Employee("101"));
employees.put("106",new Employee("106"));
employees.put("108",new Employee("108"));

从地图中检索任何对象

employees.get("101"); // will return your Employee 101