Analyze the following code. Please select all that apply. public class Test { public static void main(String[] args) { Object a1 = new A(); Object a2 = new Object(); System.out.println(a1); System.out.println(a2); } } class A { int x; @Override public String toString() { return "A's x is " + x; } } Group of answer choicesThe program cannot be compiled, because System.out.println(a1) is wrong and it should be replaced by System.out.println(a1.toString());When executing System.out.println(a1), the toString() method in the Object class is invoked.When executing System.out.println(a2), the toString() method in the Object class is invoked.When executing System.out.println(a1), the toString() method in the A class is invoked.
Question
Analyze the following code. Please select all that apply. public class Test { public static void main(String[] args) { Object a1 = new A(); Object a2 = new Object(); System.out.println(a1); System.out.println(a2); } } class A { int x; @Override public String toString() { return "A's x is " + x; } } Group of answer choicesThe program cannot be compiled, because System.out.println(a1) is wrong and it should be replaced by System.out.println(a1.toString());When executing System.out.println(a1), the toString() method in the Object class is invoked.When executing System.out.println(a2), the toString() method in the Object class is invoked.When executing System.out.println(a1), the toString() method in the A class is invoked.
Solution
The correct answers are:
- When executing System.out.println(a1), the toString() method in the A class is invoked.
- When executing System.out.println(a2), the toString() method in the Object class is invoked.
Explanation:
- The program can be compiled and run without any errors. In Java, when you try to print an object using System.out.println(), it automatically calls the toString() method of that object. So, System.out.println(a1) is not wrong and it doesn't need to be replaced by System.out.println(a1.toString()).
- When System.out.println(a1) is executed, the toString() method in the A class is invoked because a1 is an instance of class A and class A has overridden the toString() method.
- When System.out.println(a2) is executed, the toString() method in the Object class is invoked because a2 is an instance of the Object class and it doesn't have a specific implementation of the toString() method in its class or any superclass other than Object.
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