The toString is supposed to return a String.
public String toString() {
return “Name: ‘” + this.name + “‘, Height: ‘” + this.height + “‘, Birthday: ‘” + this.bDay + “‘”;
}
I suggest you make use of your IDE’s features to generate the toString method. Don’t hand-code it.
For instance, Eclipse can do so if you simply right-click on the source code and select Source > Generate toString
Java toString() method
If you want to represent any object as a string, toString() method comes into existence.
The toString() method returns the string representation of the object.
If you print any object, java compiler internally invokes the toString() method on the object. So overriding the toString() method, returns the desired output, it can be the state of an object etc. depends on your implementation.
Advantage of Java toString() method
By overriding the toString() method of the Object class, we can return values of the object, so we don’t need to write much code.
Output without toString() method
class Student{
int id;
String name;
String address;
Student(int id, String name, String address){
this.id=id;
this.name=name;
this.address=address;
}
public static void main(String args[]){
Student s1=new Student(100,”Joe”,”success”);
Student s2=new Student(50,”Jeff”,”fail”);
System.out.println(s1);//compiler writes here s1.toString()
System.out.println(s2);//compiler writes here s2.toString()
}
}
Output:Student@2kaa9dc
Student@4bbc148
You can see in the above example #1. printing s1 and s2 prints the Hashcode values of the objects but I want to print the values of these objects. Since java compiler internally calls toString() method, overriding this method will return the specified values. Let’s understand it with the example given below:
Example#2
Output with overriding toString() method
class Student{
int id;
String name;
String address;
Student(int id, String name, String address){
this.id=id;
this.name=name;
this.address=address;
}
//overriding the toString() method
public String toString(){
return id+” “+name+” “+address;
}
public static void main(String args[]){
Student s1=new Student(100,”Joe”,”success”);
Student s2=new Student(50,”Jeff”,”fail”);
System.out.println(s1);//compiler writes here s1.toString()
System.out.println(s2);//compiler writes here s2.toString()
}
}
Output:100 Joe success
50 Jeff fail
Note that toString() mostly is related to the concept of polymorphism in Java.
In, Eclipse, try to click on toString() and right click on it.Then, click on Open Declaration and see where the Superclass toString() comes from.