list集合去除重复对象

对象重复是指对象里面的变量的值都相等，并不定是地址。list集合存储的类型是基础类型还比较好办，直接把list集合转换成set集合就会自动去除。

 

当set集合存储的是对象类型时，就需要在对象的实体类里面重写public boolean equals(Object obj) {} 和 public int hashCode() {} 两个方法。

 

代码实例：

public class Student {
    public String id;
    public String name;
    public Student() {
    }
    public Student(String id,String name) {
        this.id = id;
        this.name = name;
    }

    // 省略get、set方法
    ......
    @Override
    public boolean equals(Object obj) {
        Student s=(Student)obj;
        return id.equals(s.id) && name.equals(s.name);
    }
 
    @Override
    public int hashCode() {
        String in = id + name;
        return in.hashCode();
    }
}

 

测试：

public class Test {
    public static void main(String[] args) {
        List<Student> stu = new ArrayList<Student>();
        stu.add(new Student("1","yi"));
        stu.add(new Student("3","san"));
        stu.add(new Student("3","san"));
        stu.add(new Student("2","er"));
        stu.add(new Student("2","er"));
        // set集合保存的是引用不同地址的对象
        Set<Student> ts = new HashSet<Student>();
        ts.addAll(stu);

        for (Student student : ts) {
            System.out.println(student.getId()+"-"+student.getName());
        }
    }
}

 

http://blog.csdn.net/emoven/article/details/12999265