class A {
    private String name;
    private String idstr;

    public String getName() {
        return name;
    }

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

    public String getIdstr() {
        return idstr;
    }

    public void setIdstr(String idstr) {
        this.idstr = idstr;
    }

    public A() {
    }

    A(String name, String idstr) {
        this.name = name;
        this.idstr = idstr;

    }

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

        if (obj != null && (obj instanceof A)) {
            A AObj = (A) obj;
            System.out.println(AObj.idstr);
            if ((this.idstr).equals(AObj.idstr)) {
                return true;

            }
        }
        return false;
    }
}

public class B {
    public static void main(String[] args) {
        A p1 = new A("孙悟空", "shanghai");
        A p2 = new A("孙行者", "xi'an");
        A p3 = new A("孙悟饭", "shanghai");
        System.out.println("p1,p2是否相等：" + p1.equals(p2));
        System.out.println("p2,p3是否相等：" + p2.equals(p3));
        System.out.println("p2,p3是否相等：" + p1.equals(p3));

    }
}

------解决方案--------------------

Java code

class A {
    private String name;
    private String idstr;
    public A(String name){
        this.name = name;
    }
    A(String name, String idstr) {
        this.name = name;
        this.idstr = idstr;
    }
    public boolean equals(Object obj) {
        if (this == obj) {
            return true;
        }
        if (obj != null && obj instanceof A) {
            A a = (A)obj;
            if (this.getName().equals(a.getName())){
                return true;
            }
        }
        return false;
    }
    public String getIdstr() {
        return idstr;
    }
    public void setIdstr(String idstr) {
        this.idstr = idstr;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
}
class Person1 extends A{
    
    public Person1(String name) {
        super(name);
    }
}
public class B {
    public static void main(String[] args) {
        A p1 = new A("孙悟空");
        A p2 = new Person1("孙悟空");
        A p3 = new A("孙悟饭");
        System.out.println("p1,p2是否相等：" + p1.equals(p2));
        System.out.println("p2,p3是否相等：" + p2.equals(p3));
    }
}
//楼主好好打基础，基础不行，写代码会很累的。