java - 从 java 集合中删除重复项

Question

public class Employee implements Comparable<Employee> {

    private int id;
    private String name;
    private String salary;
    private String recordStatus;
    private int key;

    public Employee(int id, String name, String salary, int key) {
        super();
        this.id = id;
        this.name = name;
        this.salary = salary;
        this.key = key;
    }
}

现在我有一个 Employee 类型的列表。

List<Employee> list = new ArrayList<Employee>();
list.add(new Employee(123, "zMadhu", "1000$",1));
list.add(new Employee(332, "bSudhan", "2000$",2));
list.add(new Employee(54, "cKongarass", "3000$",3));
list.add(new Employee(54, "xKongarass", "3000$",4));
list.add(new Employee(54, "aKongarass", "3000$",5));

现在我想从此列表中删除数据并只拥有唯一的 IDS。 IE。我预计另一个 Employee 类型列表中有 54,123,332 个。

想看看我该怎么做。非常感谢您的帮助。

Answer 1

第一次覆盖equals(..)和hashCode()您只使用 id 的地方:

...

@Override
public boolean equals(Object o) {
    if (this == o) return true;
    if (!(o instanceof Employee)) return false;

    Employee employee = (Employee) o;

    return id == employee.id;
}

@Override
public int hashCode() {
    return id;
}
...

第二只需创建一个 Set<Employee> 它不会接受重复的对象，如下所示:

Set<Employee> result = new HashSet<>(list);// [54, 123, 332]

<小时/>

看一个简单的Ideone demo