String Fumble Example

The following program excerpt is an exercise about String operations. The program tries to compare, compare (ignoring case difference) and copy Strings. Please refer to the comments for the motivation. However, there are some mistakes, which may make the program inconsistent with the intention of the programmer. Please try your best to find these mistakes before reading the questions.

Download files: StringFumbles.java
Areas: if statements.

StringFumbles.java

1	/** This Java code contains some common errors.
2	* Can you find the errors and correct them?
3	*/
4
5	String firstStr = "I am Canadian";
6	String secondStr = "Canadian";
7
8	String thirdStr = "I am " + secondStr;
9	System.out.println("thirdStr is " + thirdStr);
10

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Question 1

Is there a problem if we change the first line of code to the following String initialization?
String firstStr = 'I am Canadian';
If so, what is it?

Question 2

After thirdStr is assigned a value, what is the String in thirdStr?

Question 3

Do firstStr and thirdStr have the same character String after the assignment statement for thirdStr?

Question 4

Does the following comparison tell us whether the character strings are the same?
if (firstStr == thirdStr)

Question 5

What is the output of the first if statement?

Question 6

How should we correct the following comparison?
if (firstStr == thirdStr)

Question 7

What does the following code do?
String fourthStr = new String(firstStr);

Question 8

What is the output of the second if statement?

Question 9

What does the following code do?
String fifthStr = firstStr;

Question 10

What is the output of the third if statement?

Question 11

Does the following String comparison have the intended effect?
if (0==firstStr.compareTo(thirdStr))

Question 12

Aside from the problem discussed in the above question, there is another problem in the last if statement. Can you find it?