Arrays and Strings - Beginning Java 2 SDK - page 139

string1 is now: Too many cooks
string1.equals(string3) is true. so strings are equal.
Test 2
string3 is now: TOO many cooks
string1 is now: Too many cooks
string1.equals(string3) is false so strings are not equal.
string1.equalsIgnoreCase(string3) is true so strings are equal ignoring case .
How It Works
Before we look in detail at how the program works, let's first take some time to look at how the method
calls that pepper the code are put together.
In the if expression, we've called the method equals() of the object string1 to test for equality with
string3 . This is the syntax we have been using to call the method println() in the object out . In
general, to call a method belonging to an object you write the object name, then a period, then the name of
the method. The parentheses following the method name enclose the information to be passed to the
method - string3 in this case. The general form for calling a method for an object is shown below.
We will learn more about this in Chapter 5, when we look at how to define our own
classes. For the moment, just note that you don't necessarily need to pass any
arguments to a method. On the other hand there can be several. It all depends on how
the method was defined in the class.
The equals() method requires one argument that you put between the parentheses. This must be the
String object that is to be compared with the original object. The method returns true if the value
passed to it ( string3 in our example) is identical to the string pointed to by the String object that
owns the method, in this case string1 . As you may have already guessed, we could just as well call the
equals() method for the object string3 , and pass string1 as the argument to compare the two
strings. In this case, the expression to call the method would be:
string3.equals(string1)
and we would get exactly the same result.
Looking at the program code, after outputting the values of string3 and string1 , the next line
shows that calling the equals() method for string1 with string3 as the argument returns true .
After the if , we make string3 reference a new string. We then compare the values of string1 and
string3 once more, and, of course, the result of the comparison is now false .
Finally we compare string1 with string3 using the equalsIgnoreCase() method. Here the
result is true since the strings only differ in the case of the first three characters.