Question

For each of the following, write a single statement that performs the indicated task: a) Compare the string in \(s 1\) to the string in \(s 2\) for equality of contents. b) Append the string \(s 2\) to the string \(s 1, u \sin g+=\) c) Determine the length of the string in \(s 1\)

Short answer

Compare: s1.equals(s2); Append: s1 += s2; Length: s1.length();

Step-by-step solution

Comparing Strings for Equality

To compare two strings for equality, use the '==' operator. The statement will look like this: 'boolean isEqual = s1.equals(s2);'. This will compare the content of 's1' and 's2' and return true if they are equal, and false otherwise.

Appending a String to Another String

To append a string to another string using the '+=', the syntax is 's1 += s2;'. This will append the content of 's2' to 's1'.

Determining the Length of a String

To determine the length of a string, use the '.length()' method. The statement is 'int length = s1.length();'. This will give you the length of the string contained in 's1'.

Key concepts

String Comparison in Java

Comparing strings in Java is a fundamental operation that is often used to check if two strings are identical in terms of their content. Unlike primitive data types such as 'int' or 'char', where you can use the '==' operator to compare values directly, with strings, using 'equals()' method is the preferred way.

When comparing strings with 's1.equals(s2)', it performs a content comparison. This means that even if 's1' and 's2' are different objects in memory, as long as the sequence of characters is exactly the same, this method will return 'true'. It's very important to remember that strings are case-sensitive, so 'Hello' and 'hello' would be considered as different. For a case-insensitive comparison, one would use 'equalsIgnoreCase()' method.

Always ensure to avoid using '==' for string content comparison because '==' checks if both objects point to the same memory location, which is not what you usually want for string comparison.

String Appending

To combine two strings in Java, we use the term 'string appending'. This operation is performed when you want to add one string to the end of another. The use of 's1 += s2' is a common shorthand that takes the string referred to by 's2' and adds it to the end of 's1'. It's equivalent to writing 's1 = s1.concat(s2);'.

String appending can be particularly useful when building a string in a loop or when you're accruing additional characters or strings to form a final result. Keep in mind that strings in Java are immutable, meaning each time you append, you're actually creating a new string rather than modifying the original one. This is fine for a small number of concatenations but can be inefficient for numerous ones. In such cases, consider using a 'StringBuilder' or 'StringBuffer' for better performance.

String Length

Knowing the length of a string is an essential aspect of string manipulation. In Java, this is achieved with the '.length()' method. Invoking 's1.length()' returns an 'int' representing the number of characters contained within the string 's1'.

This method is frequently used in situations where you need to traverse the content of a string character by character, or when validating input to ensure that it meets certain criteria such as minimum or maximum length. Remember, the '.length()' method counts characters and not bytes, so even if you have special or Unicode characters, they will be appropriately counted as single characters in the length calculation.