List去重-蒲公英云

List去重

我们知道List允许有相同的元素，那么我们怎么通过方法来让它去重呐，
我们都会想到Set集合，Set集合是不允许有相同的元素的，所以我们可以借助Set集合，把重复的元素去掉。如果不是对象类型的去重。直接用Set集合转化就行。就像下面的

List list = new ArrayList();
        list.add("aa");
        list.add("dd");
        list.add("cc");
        list.add("aa");
        Set set = new HashSet();
        set.addAll(list);
        List n = new ArrayList<>();
        n.addAll(set);
        System.out.println(n);
结果：
    [aa, dd, cc]
    通过这，你会发现可以啊
    但是对象呐，
public class People {
    private String name;
    private String phoneNumber;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getPhoneNumber() {
        return phoneNumber;
    }
    public void setPhoneNumber(String phoneNumber) {
        this.phoneNumber = phoneNumber;
    }
    public People(String name, String phoneNumber) {
        super();
        this.name = name;
        this.phoneNumber = phoneNumber;
}
    @Override
    public String toString() {
        return "People{" +
                "name='" + name + ''' +
                ", phoneNumber='" + phoneNumber + ''' +
                '}';
    }
}

这种需要重写equals和hashcode，再用Set去重。

public class People {
    private String name;
    private String phoneNumber;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getPhoneNumber() {
        return phoneNumber;
    }
    public void setPhoneNumber(String phoneNumber) {
        this.phoneNumber = phoneNumber;
    }
    public People(String name, String phoneNumber) {
        super();
        this.name = name;
        this.phoneNumber = phoneNumber;
}
    @Override
    public String toString() {
        return "People{" +
                "name='" + name + ''' +
                ", phoneNumber='" + phoneNumber + ''' +
                '}';
    }
    @Override
    public boolean equals(Object arg0) {
        // TODO Auto-generated method stub
        People p = (People) arg0;
        return name.equals(p.name) && phoneNumber.equals(p.phoneNumber);
    }
    @Override
    public int hashCode() {
        // TODO Auto-generated method stub
        String str = name + phoneNumber;
        return str.hashCode();
    }
}

这里注意一下重写equals方法和hashcode方法

public boolean equals(Object orgs){
        // 强制类型转换
        People p = (People)orgs;
        return p.name.equals( name )&& p.phoneNumber.equals(phoneNumber);
    }
    public int hashcode(){
        String str = name + phoneNumber;
        return str.hashCode();
    }