问题
Is there a way to make toString() include private fields of the super class? I tried adding a super.toString(), no use however.
Please see the code below
Employee.java
package test;
public class Employee {
private String name;
private int id;
private double salary;
public Employee(String name, int id, double salary) {
super();
this.name = name;
this.id = id;
this.salary = salary;
}
public double getSalary() {
return salary;
}
@Override
public String toString() {
return "Employee [name=" + name + ", id=" + id + ", salary=" + salary
+ "]";
}
public static void main(String[] args) {
Employee e=new Employee("Joe", 14, 5000);
System.out.println(e);
Manager m=new Manager("Bill", 23, 5000, 10);
System.out.println(m);
System.out.println("Employee Salary is "+e.getSalary()+"\nManager salary is "+m.getSalary());
}
}
Manager.java
package test;
public class Manager extends Employee{
private double bonus;
public Manager(String name, int id, double salary,int bonus) {
super(name, id, salary);
this.bonus=bonus;
}
public double getSalary()
{
double baseSalary=super.getSalary();
return (baseSalary+baseSalary*(bonus/100));
}
@Override
public String toString() {
return(this.getClass().getName()+" ["+super.toString().substring((this.getClass().getSuperclass().getName().length()-3
), (super.toString().length())-1)+", bonus="+bonus+"]");
//didn't work
//super.toString();
//return "Manager [bonus=" + bonus + "]";
}
}
Output
Employee [name=Joe, id=14, salary=5000.0]
test.Manager [name=Bill, id=23, salary=5000.0, bonus=10.0]
Employee Salary is 5000.0
Manager salary is 5500.0
That was the best i could do , to concatenate super.toString()+' a set of Strings', surely this is messy , is there some other way , even if the language spec does not allow it does eclipse have some facility to do that , NOTE: I used eclipse to generate the toString method , any way by which i can tell eclipse to include the super class fields too,
In other words can i replace this messy code
return(this.getClass().getName()+" ["+super.toString().substring((this.getClass().getSuperclass().getName().length()-3
), (super.toString().length())-1)+", bonus="+bonus+"]");
by getting eclipse to automate the process and generate a suitable way to do it?
回答1:
If you create getters and setters in your superclass then you can acces the variables through those methods. Other possibility is to change the visibility from private to protected
first solution looks like this
Employee
public class Employee {
private String name;
private int id;
private double salary;
public Employee(String name, int id, double salary) {
super();
this.name = name;
this.id = id;
this.salary = salary;
}
public double getSalary() {
return salary;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public void setSalary(double salary) {
this.salary = salary;
}
@Override
public String toString() {
return "Employee [name=" + name + ", id=" + id + ", salary=" + salary + "]";
}
}
Manager
public class Manager extends Employee {
private double bonus;
public Manager(String name, int id, double salary, int bonus) {
super(name, id, salary);
this.bonus = bonus;
}
public double getSalary() {
double baseSalary = super.getSalary();
return (baseSalary + baseSalary * (bonus / 100));
}
@Override
public String toString() {
return "Manager [name=" + getName() + ", id=" + getId() + ", salary=" + getSalary() + ", bonus=" + bonus + "]";
}
}
Second one (using protected)
Employee
public class Employee {
protected String name;
protected int id;
protected double salary;
public Employee(String name, int id, double salary) {
super();
this.name = name;
this.id = id;
this.salary = salary;
}
public double getSalary() {
return salary;
}
@Override
public String toString() {
return "Employee [name=" + name + ", id=" + id + ", salary=" + salary + "]";
}
}
Manager
public class Manager extends Employee {
protected double bonus;
public Manager(String name, int id, double salary, int bonus) {
super(name, id, salary);
this.bonus = bonus;
}
public double getSalary() {
double baseSalary = super.getSalary();
return (baseSalary + baseSalary * (bonus / 100));
}
@Override
public String toString() {
return "Manager [name=" + name + ", id=" + id + ", salary=" + salary + ", bonus=" + bonus + "]";
}
}
Personally i'd use the getter/setter method but it's up to you.
EDIT: Additonal to eclipse generation of toString() in eclipse.
You can't seem to generate it with getters and setter (just had a quick look, you can see some documentation here.
What I did figure out is how you can edit the Code Template used when generating the toString() so it includes the toString() from the superclass.
When you enter the generate toString() dialog there is a field 'String Format' with <Default Template> next to it. when you click the edit button you can create a new Code Template.
This template automatically holds the <Default Template> and should look something like this:
${object.className} [${member.name()}=${member.value}, ${otherMembers}]
only thing you'll have to add is the following at the end
[super: ${object.superToString}]
This way it'll display the toString() form the superclass
回答2:
You can let eclipse generate it, however it would not look like you want it.
which creates this code:
public String toString() {
return "Manager [bonus=" + bonus + ", toString()=" + super.toString() + "]";
}
which would print this:
Manager [bonus=10.0, toString()=Employee [name=Bill, id=23, salary=5000.0]]
That's the most you can make eclipse generate for you.
You can clean it up a little so it would look like this
public String toString() {
return "Manager [bonus=" + bonus + "] is a " + super.toString();
}
which would print
Manager [bonus=10.0] is a Employee [name=Bill, id=23, salary=5000.0]
However, your custom solution works as well. So why not use it?
You can clean it up a little like this:
@Override
public String toString() {
return "Manager [" + superFieldsFromToString() + ", bonus=" + bonus + "]";
}
private String superFieldsFromToString() {
String superToString = super.toString();
int superClassNameLength = getClass().getSuperclass().getSimpleName().length();
int fieldStartIdx = superClassNameLength + 2; // + 2 removes " ["
int fieldEndIdx = superToString.length() - 1; // - 1 removes "]"
return superToString.substring(fieldStartIdx , fieldEndIdx);
}
which outputs
Manager [name=Bill, id=23, salary=5000.0, bonus=10.0]
The only other options, as others have mentioned, are to use reflection to access the private fields, make the fields protected or create public getters.
I would not advice to do any of this, as your class design should not be defined by debug output.
回答3:
No. Because if you could directly access private fields of super class, those fields would not be private.
回答4:
There is something that doesn't make sense:
All your fields are either primitives and immutable thus you can safely publish (For Concurenecy purposes) them using getters.
If you have in mind making salary, id, bonus private because these should not be known(and thus not provide getters), then why provide a toString that shows this secrete information. If the toString is just for visual testing purposes, then consider making them protected and then put them private again when you have successfully tested your class.
Otherwise, there is something wrong in the structure of your classes and you are just trying to do some hacks in the language.
回答5:
The possible solution is to make a protected getters for fields in case you don't want to make fields itself protected.
回答6:
Best Solution
You can call the getters for the super class instance variables and put the values on your toString(). You could even be sneaky and make the getters protected so that only the child classes can view the variable's value.
Lazy Solution
Make the fields protected which might be a bad idea depending on how your super class is designed.
Bad Idea
You could also use reflection, but I wouldn't do that.
Reflection was created for a specific purpose, to discover the functionality of a class that was unknown at compile time, similar to what the dlopen and dlsym functions do in C. Any use outside of that should be heavily scrutinized. (https://softwareengineering.stackexchange.com/questions/193526/is-it-a-bad-habit-to-overuse-reflection)
回答7:
If you can't change the code of the super class (change scope of members or add a getter), then you can use the Java reflection API to access a private field:
Manager managerObject = new managerObject():
Employee e = (Employee) managerObject;
Field f = e.getClass().getDeclaredField("salary");
f.setAccessible(true);
double sal = (double) f.get(e);
来源：https://stackoverflow.com/questions/27143951/how-make-tostring-method-return-super-class-private-fields-also-along-with-its