在Java中打印出多个对象的属性

Question

I have created a person class, with attributes age and name. I have created 5 instances of the class in an object array as well, and would like to print the attributes out with a for loop. It is my understanding that toString is explicitly called when you try to print out an object, so I override toString so that it prints out both attributes of the object when it is called.

Here is my code:

class Person
{
    int age;
    String name;

    public Person(String name, int age)
    {
        this.age = age;
        this.name = name;
    }


    public String toString(Person p)
    {
        return "Name: " + p.name +"Age: "+ p.age;
    }
}


public class P1Q5Bubble {

public static void main(String[] args) {

        Person [] pp = new Person [5];

        pp[0] = new Person("Andy" , 18);
        pp[1] = new Person("Lisa" , 20);
        pp[2] = new Person("Bob" , 10);
        pp[3] = new Person("Eva" , 18);
        pp[4] = new Person("Tim" , 13);       




        for(int i = 0; i> pp.length ; i++)
            System.out.println(pp[i]);
}

Answer 1

You need to change two things

1) in for i > pp.length to i < pp.length

2) toString() method used in System.out.print or System.out.println doesn't have arguments so change it to something like

public String toString() {
    return "Name: " + name + "Age: " + age;
}

Answer 2

Your for loop terminating condition is incorrect, you need i < pp.length .

Using i > pp.length your loop will execute no statements. The loop will only execute so long as the terminating condition is true .

Furthermore you're not overriding toString correctly: your toString method shouldn't take any arguments: your instance variables name and age will be available to the function.

Answer 3

The toString() function which you need to override in Person class should not contain any argument (since the Object class in which it is defined does not contain an argument). The corrected code for that function will be

@Override public String toString()
{
   return return "Name: " + name +"Age: "+ age;
}

Answer 4

You should override default toString() (with no arguments) instead you have added a new method. So remove that argument and use 'this' in place of person argument