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Section 7.12 Chapter Summary

Subsection 7.12.1 Technical Terms

baseline concatenation copy cosntructor
data structure delimited string delimiter
empty string garbage collection glyph
lexicographic order logical font off-by-one error
orphan object physical font read only
string string index string literal
token unit indexed zero indexed

Subsection 7.12.2 Important Points}

  • A String literal is a sequence of 0 or more characters enclosed within double quotation marks. A String object is a sequence of 0 or more characters, plus a variety of class and instance methods and variables.

  • A String object is created automatically by Java the first time it encounters a literal string, such as “Socrates,” in a program. Subsequent occurrences of the literal do not cause additional objects to be instantiated. Instead, every occurrence of the literal “Socrates” refers to the initial object.

  • A String object is created whenever the new operator is used in conjunction with a String() constructor—for example, new String("hello").

  • The String concatenation operator is the overloaded \(+\) symbol; it is used to combine two String s into a single String: “hello” + “world” ==> “helloworld”. Strings are indexed starting at 0. The indexOf() and lastIndexOf() methods are used for finding the first or last occurrence of a character or substring within a String. The valueOf() methods convert a nonstring into a String. The length() method determines the number of characters in a String. The charAt() method returns the single character at a particular index position. The various substring() methods return the substring at particular index positions in a String.

  • The overloaded equals() method returns true if two String s contain the same exact sequence of characters. The == operator, when used on String s, returns true if two references designate the same String object. String objects are immutable. They cannot be modified.

  • A StringBuffer is a string object that can be modified using methods such as insert() and append().

  • A StringTokenizer is an object that can be used to break a String into a collection of tokens separated by delimiters. The whitespace characters—tabs, blanks, and newlines—are the default delimiters.

  • The FontMetrics class is used to obtain the specific dimensions of the the various Font s. It is useful when you wish to center text. Font s are inherently platform dependent. For maximum portability, it is best to use default fonts.

Solutions 7.12.3 Solutions to Self-Study Exercises

7.2 String Basics
7.2.1 Constructing Strings

Self-Study Exercises
7.2.1.3. Creating an empty string.

7.2.2 Concatenating Strings

Self-Study Exercises

7.2.4 Converting Data to Strings

Self-Study Exercises

7.3 Finding Things Within a String
7.3.1 indexOf()

Self-Study Exercises
7.3.1.1. String indexOf() expressions.
7.3.1.2. String indexOf() expressions.
7.3.1.3. String indexOf() expressions.
7.3.1.4. String indexOf() expressions.
7.3.1.5. Tricky indexOf() expression.

7.4 Example: Keyword Search
7.4.2 Testing and Debugging

Self-Study Exercise

7.5 From the Java Library: java.lang.StringBuffer

Self-Study Exercise

7.6 Retrieving Parts of Strings
7.6.1 charAt() and subString() methods

Self-Study Exercises

7.8 Processing Each Character in a String
7.8.5 Example: Capitalizing the First Letter

Self-Study Exercises

7.9 Comparing Strings
7.9.1 Lexicographic Order

Self-Study Exercises

7.9.3 String Identity Versus String Equality

Self-Study Exercises
7.9.3.1. String equality vs identity.
7.9.3.2. String equality vs identity Part 2.
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