public class Student {
    private String name;

    private int age;

    public boolean equals(Object o) {
        boolean flag = false;
        if (o != null) {
            if (this == o) {
                flag = true;
            } else {
                if (o instanceof Student) {
                    Student s = (Student) o;
                    if (this.name.equals(s.name) && this.age == s.age) {
                        flag = true;
                    }
                }
            }
        }
        return flag;
    }

    public static void main(String[] args) {
        Student s1 = new Student();
        s1.name = "kaka";
        s1.age = 10;
        Student s2 = new Student();
        s2.name = "kaka";
        s2.age = 10;
        System.out.println(s1.equals(s2));
    }
}

public class Student
{
    private String name;

    private int age;

    public boolean equals(Object o)
    {
        boolean flag = false;

        if(o != null)
        {
            if(this == o)
            {
                flag = true;
            }
            else if(o instanceof Student)
            {
                Student s = (Student)o;

                if(this.name.equals(s.name) && this.age == s.age)
                {
                    flag = true;
                }
            }
        }
        
        return flag;
    }

    public static void main(String[] args)
    {
        Student s1 = new Student();
        s1.name = "kaka";
        s1.age = 10;
        Student s2 = new Student();
        s2.name = "kaka";
        s2.age = 10;
        System.out.println(s1.equals(s2));
    }
}

------解决方案--------------------
Java code
    public boolean equals(Object obj) {
        if (obj == this)
            return true;
        if (!(obj instanceof Student))
            return false;
        Student s = (Student) obj;
        return this.name.equals(s.name) && this.age == s.age;
    }

------解决方案--------------------
用o.getClass()==Student.class 会不会更精确一点

------解决方案--------------------

还可以更好一点
Java code


public boolean equals(Object obj) {
  if (this == obj) return true;
  
  if (obj == null) return false;

  if (getClass() != obj.getClass()) return false; 
  //注意,这里如果用 (obj instanceof Student) 来判断的话,那么Student所有的子类
  //的 equals 方法就不能有改变

  Student s = (Student) obj;

  return name.equals(s.name) && age == s.age;  

}

------解决方案--------------------
Java code
    public boolean equals(Object obj) {
        if (obj == this) return true;
        if (obj == null) return false;
        if (obj.getClass() != this.getClass()) return false;
        Student other = (Student) obj;
        return (other.name == null ? this.name == null : other.name.equals(this.name)) &&
               (other.age == this.age);
    }