Consider a class that uses the following variables to implement an array-based stack:
String [ ] s = new String[100];
Int top = -1;// Note top == -1 indicates stack is empty
A method that implements a String peek()operation can be written as
A) if (top == -1)
Throw new RuntimeException("Empty Stack");
Else
Return s[top -1];
B) if (top -1.
Return s[top];
Else
Throw new RuntimeException("Empty Stack".;
C) top --;
If (top == -1.
Throw new RuntimeException("Empty Stack".;
Else
Return s[top];
D) if (top == 0.
Throw new RuntimeException("Empty Stack".;
Else
{
Top --;
Return s[top];
}

Question

Consider a class that uses the following variables to implement an array-based stack:
String [ ] s = new String[100];
Int top = -1;// Note top == -1 indicates stack is empty
A method that implements a String peek()operation can be written as
A) if (top == -1)
Throw new RuntimeException("Empty Stack");
Else
Return s[top -1];
B) if (top > -1.
Return s[top];
Else
Throw new RuntimeException("Empty Stack".;
C) top --;
If (top == -1.
Throw new RuntimeException("Empty Stack".;
Else
Return s[top];
D) if (top == 0.
Throw new RuntimeException("Empty Stack".;
Else
{
Top --;
Return s[top];
}

Quizplus · Accepted Answer

This method checks if the stack is empty by checking if the top index is greater than -1 (i.e. not equal to -1). If it is not empty, it returns the element at the top index. If it is empty, it throws a RuntimeException with the message "Empty Stack". This is the best choice because it correctly handles both cases of the stack being empty or not empty without relying on manipulating the top index. Option A is incorrect because it returns the element at index top-1 instead of top, which is not necessarily the correct element. Option C is incorrect because it decrements the top index before returning the element, which can lead to the incorrect element being returned. Option D is incorrect because it checks if top is equal to 0 instead of -1, and also decrements top before returning the element.

Consider a Class That Uses the Following Variables to Implement