Java student类

Java求学生类
为什么运行后一片空白，应该如何修改，才能够得到我想要的效果

public class Student {

    private long id;
    private String name;
    private int age;
    private boolean sex;
    private String phone;

    public Student(){

    }
    public Student(long i ,String n,Boolean s,String p){
        super();
        this.id = i;
        this.name = n;
        this.sex = s;
        this.phone = p;
    }

    @Override
    public String toString() {
        return this.name + ":" + this.phone;
    }

    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public boolean isSex() {
        return sex;
    }

    public void setSex(boolean sex) {
        this.sex = sex;
    }

    public String getPhone() {
        return phone;
    }

    public void setPhone(String phone) {
        this.phone = phone;
    }
}

在main函数里new一个学生类，例如:Student a = new Student(括号里是你所传进去的参数)。
然后在toString()里面写出打印内容。
最后在mian函数里调用a.toString()方法即可。