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Page 1: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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Strings and Text I/O

Page 2: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

2

Motivations

Often you encounter the problems that involve string processing and file input and output. Suppose you need to write a program to replace all occurrences of a word with a new word in a file. How do you solve this problem? This chapter introduces strings and text files, which will enable you to solve this problem.

Page 3: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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Objectives To use the String class to process fixed strings. To use the Character class to process a single character. To use the StringBuilder/StringBuffer class to process flexible

strings. To learn how to pass arguments to the main method from the

command line. To discover file properties and to delete and rename files using

the File class. To write data to a file using the PrintWriter class. To read data from a file using the Scanner class.

Page 4: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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The String Class Constructing a String:

– String message = "Welcome to Java“;– String message = new String("Welcome to Java“);

– String s = new String(); Obtaining String length and Retrieving Individual Characters in

a string String Concatenation (concat) Substrings (substring(index), substring(start, end)) Comparisons (equals, compareTo) String Conversions Finding a Character or a Substring in a String Conversions between Strings and Arrays Converting Characters and Numeric Values to Strings

Page 5: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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Constructing Strings

String newString = new String(stringLiteral);

 

String message = new String("Welcome to Java");

Since strings are used frequently, Java provides a shorthand initializer for creating a string:

String message = "Welcome to Java";

Page 6: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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Strings Are ImmutableA String object is immutable; its contents cannot be changed. Does the following code change the contents of the string?

String s = "Java";

s = "HTML";

Page 7: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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Trace Code

String s = "Java";

s = "HTML";

: String

String object for "Java"

s

After executing String s = "Java";

After executing s = "HTML";

: String

String object for "Java"

: String

String object for "HTML"

Contents cannot be changed

This string object is now unreferenced

s

animation

Page 8: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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Trace Code

String s = "Java";

s = "HTML";

: String

String object for "Java"

s

After executing String s = "Java";

After executing s = "HTML";

: String

String object for "Java"

: String

String object for "HTML"

Contents cannot be changed

This string object is now unreferenced

s

animation

Page 9: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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Interned StringsSince strings are immutable and are frequently used, to improve efficiency and save memory, the JVM uses a unique instance for string literals with the same character sequence. Such an instance is called interned. For example, the following statements:

Page 10: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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Examples

display

  s1 == s is false

s1 == s3 is true

A new object is created if you use the new operator. If you use the string initializer, no new object is created if the interned object is already created.

String s1 = "Welcome to Java"; String s2 = new String("Welcome to Java"); String s3 = "Welcome to Java"; System.out.println("s1 == s2 is " + (s1 == s2)); System.out.println("s1 == s3 is " + (s1 == s3));

: String

Interned string object for "Welcome to Java"

: String

A string object for "Welcome to Java"

s1

s2

s3

Page 11: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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Trace Code String s1 = "Welcome to Java"; String s2 = new String("Welcome to Java"); String s3 = "Welcome to Java";

: String

Interned string object for "Welcome to Java"

s1

animation

Page 12: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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Trace Code String s1 = "Welcome to Java"; String s2 = new String("Welcome to Java"); String s3 = "Welcome to Java";

: String

Interned string object for "Welcome to Java"

: String

A string object for "Welcome to Java"

s1

s2

Page 13: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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Trace Code String s1 = "Welcome to Java"; String s2 = new String("Welcome to Java"); String s3 = "Welcome to Java";

: String

Interned string object for "Welcome to Java"

: String

A string object for "Welcome to Java"

s1

s2

s3

Page 14: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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String Comparisons

java.lang.String

+equals(s1: String): boolean

+equalsIgnoreCase(s1: String): boolean

+compareTo(s1: String): int

+compareToIgnoreCase(s1: String): int

+startsWith(prefix: String): boolean

+endsWith(suffix: String): boolean

Returns true if this string is equal to string s1.

Returns true if this string is equal to string s1 case-insensitive.

Returns an integer greater than 0, equal to 0, or less than 0 to indicate whether this string is greater than, equal to, or less than s1.

Same as compareTo except that the comparison is case-insensitive.

Returns true if this string starts with the specified prefix.

Returns true if this string ends with the specified suffix.

Page 15: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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String Comparisons equals

String s1 = new String("Welcome“);String s2 = "welcome";

if (s1.equals(s2)){ // s1 and s2 have the same contents }

if (s1 == s2) { // s1 and s2 have the same reference }

Page 16: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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String Comparisons, cont. compareTo(Object object)

String s1 = new String("Welcome“);String s2 = "welcome";

if (s1.compareTo(s2) > 0) { // s1 is greater than s2 } else if (s1.compareTo(s2) == 0) { // s1 and s2 have the same contents } else // s1 is less than s2

Page 17: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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String Length, Characters, and Combining Strings

java.lang.String

+length(): int

+charAt(index: int): char

+concat(s1: String): String

Returns the number of characters in this string.

Returns the character at the specified index from this string.

Returns a new string that concatenate this string with string s1. string.

Page 18: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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Finding String Length

Finding string length using the length() method:

message = "Welcome";

message.length() (returns 7)

Page 19: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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Retrieving Individual Characters in a String

Do not use message[0]

Use message.charAt(index)

Index starts from 0

W e l c o m e t o J a v a

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

message

Indices

message.charAt(0) message.charAt(14) message.length() is 15

Page 20: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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String Concatenation

String s3 = s1.concat(s2);

String s3 = s1 + s2;

s1 + s2 + s3 + s4 + s5 same as

(((s1.concat(s2)).concat(s3)).concat(s4)).concat(s5);

Page 21: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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Extracting Substrings

java.lang.String

+subString(beginIndex: int): String

+subString(beginIndex: int, endIndex: int): String

Returns this string’s substring that begins with the character at the specified beginIndex and extends to the end of the string

.

Returns this string’s substring that begins at the specified beginIndex and extends to the character at index endIndex – 1. Note that the character at endIndex is not part of the substring.

Page 22: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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Extracting Substrings

You can extract a single character from a string using the charAt method. You can also extract a substring from a string using the substring method in the String class.

String s1 = "Welcome to Java";String s2 = s1.substring(0, 11) + "HTML";

W e l c o m e t o J a v a

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

message

Indices

message.substring(0, 11) message.substring(11)

Page 23: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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Converting, Replacing, and Splitting Strings

java.lang.String

+toLowerCase(): String

+toUpperCase(): String

+trim(): String

+replace(oldChar: char, newChar: char): String

+replaceFirst(oldString: String, newString: String): String

+replaceAll(oldString: String, newString: String): String

+split(delimiter: String): String[]

Returns a new string with all characters converted to lowercase.

Returns a new string with all characters converted to uppercase.

Returns a new string with blank characters trimmed on both sides.

Returns a new string that replaces all matching character in this string with the new character.

Returns a new string that replaces the first matching substring in this string with the new substring.

Returns a new string that replace all matching substrings in this string with the new substring.

Returns an array of strings consisting of the substrings split by the delimiter.

Page 24: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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Examples"Welcome".toLowerCase() returns a new string, welcome.

"Welcome".toUpperCase() returns a new string, WELCOME.

" Welcome ".trim() returns a new string, Welcome.

"Welcome".replace('e', 'A') returns a new string, WAlcomA.

"Welcome".replaceFirst("e", "AB") returns a new string, WABlcome.

"Welcome".replace("e", "AB") returns a new string, WABlcomAB.

"Welcome".replace("el", "AB") returns a new string, WABlcome.

Page 25: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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Splitting a String

String[] tokens = "Java#HTML#Perl".split("#", 0);

for (int i = 0; i < tokens.length; i++)

System.out.print(tokens[i] + " ");

Java HTML Perl

displays

Page 26: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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Matching, Replacing and Splitting by Patterns You can match, replace, or split a string by specifying a pattern. This is an extremely useful and powerful feature, commonly known as regular expression. Regular expression is complex to beginning students. For this reason, two simple patterns are used in this section.

"Java".matches("Java");

"Java".equals("Java");

"Java is fun".matches("Java.*");

"Java is cool".matches("Java.*");

Page 27: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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Matching, Replacing and Splitting by Patterns The replaceAll, replaceFirst, and split methods can be used with a regular expression. For example, the following statement returns a new string that replaces $, +, or # in "a+b$#c" by the string NNN.

String s = "a+b$#c".replaceAll("[$+#]", "NNN");

System.out.println(s);

Here the regular expression [$+#] specifies a pattern that matches $, +, or #. So, the output is aNNNbNNNNNNc.

Page 28: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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Matching, Replacing and Splitting by Patterns The following statement splits the string into an array of strings delimited by some punctuation marks.

String[] tokens = "Java,C?C#,C++".split("[.,:;?]"); for (int i = 0; i < tokens.length; i++) System.out.println(tokens[i]);

Page 29: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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Finding a Character or a Substring in a String

java.lang.String

+indexOf(ch: char): int

+indexOf(ch: char, fromIndex: int): int

+indexOf(s: String): int

+lastIndexOf(ch: int): int

+lastIndexOf(s: String): int

Returns the index of the first occurrence of ch in the string. Returns -1 if not matched.

Returns the index of the first occurrence of ch after fromIndex in the string. Returns -1 if not matched.

Returns the index of the first occurrence of string s in this string. Returns -1 if not matched.

Returns the index of the last occurrence of ch in the string. Returns -1 if not matched.

Returns the index of the last occurrence of string s. Returns -1 if not matched.

Page 30: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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Finding a Character or a Substring in a String

"Welcome to Java".indexOf('W') returns 0.

"Welcome to Java".indexOf('x') returns -1.

"Welcome to Java".indexOf('o', 5) returns 9.

"Welcome to Java".indexOf("come") returns 3.

"Welcome to Java".indexOf("Java", 5) returns 11.

"Welcome to Java".indexOf("java", 5) returns -1.

"Welcome to Java".lastIndexOf('a') returns 14.

Page 31: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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Convert Character and Numbers to Strings

The String class provides several static valueOf methods for converting a character, an array of characters, and numeric values to strings. These methods have the same name valueOf with different argument types char, char[], double, long, int, and float. For example, to convert a double value to a string, use String.valueOf(5.44). The return value is string consists of characters ‘5’, ‘.’, ‘4’, and ‘4’.

Page 32: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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Problem: Finding Palindromes

Objective: Checking whether a string is a palindrome: a string that reads the same forward and backward.

CheckPalindromeCheckPalindrome RunRun

Page 33: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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The Character Class

java.lang.Character

+Character(value: char)

+charValue(): char

+compareTo(anotherCharacter: Character): int

+equals(anotherCharacter: Character): boolean

+isDigit(ch: char): boolean

+isLetter(ch: char): boolean

+isLetterOrDigit(ch: char): boolean

+isLowerCase(ch: char): boolean

+isUpperCase(ch: char): boolean

+toLowerCase(ch: char): char

+toUpperCase(ch: char): char

Constructs a character object with char value

Returns the char value from this object

Compares this character with another

Returns true if this character equals to another

Returns true if the specified character is a digit

Returns true if the specified character is a letter

Returns true if the character is a letter or a digit

Returns true if the character is a lowercase letter

Returns true if the character is an uppercase letter

Returns the lowercase of the specified character

Returns the uppercase of the specified character

Page 34: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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Examples

Character charObject = new Character('b');

charObject.compareTo(new Character('a')) returns 1charObject.compareTo(new Character('b')) returns 0charObject.compareTo(new Character('c')) returns -1charObject.compareTo(new Character('d') returns –2charObject.equals(new Character('b')) returns truecharObject.equals(new Character('d')) returns false

Page 35: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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Problem: Counting Each Letter in a String

This example gives a program that counts the number of occurrence of each letter in a string. Assume the letters are not case-sensitive.

CountEachLetterCountEachLetter RunRun

Page 36: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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StringBuilder and StringBuffer

The StringBuilder/StringBuffer class is an alternative to the String class. In general, a StringBuilder/StringBuffer can be used wherever a string is used. StringBuilder/StringBuffer is more flexible than String. You can add, insert, or append new contents into a string buffer, whereas the value of a String object is fixed once the string is created.

Page 37: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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StringBuilder Constructors

java.lang.StringBuilder

+StringBuilder()

+StringBuilder(capacity: int)

+StringBuilder(s: String)

Constructs an empty string builder with capacity 16.

Constructs a string builder with the specified capacity.

Constructs a string builder with the specified string.

Page 38: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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Modifying Strings in the Builder java.lang.StringBuilder

+append(data: char[]): StringBuilder +append(v: aPrimitiveType): StringBuilder

+append(s: String): StringBuilder

+delete(startIndex: int, endIndex: int): StringBuilder

+deleteCharAt(index: int): StringBuilder

+insert(offset: int, data: char[]): StringBuilder

+insert(offset: int, b: aPrimitiveType): StringBuilder

+insert(offset: int, s: String): StringBuilder

+replace(startIndex: int, endIndex: int, s: String): StringBuilder

+reverse(): StringBuilder

+setCharAt(index: int, ch: char): void

Appends a char array into this string builder. Appends a primitive type value as a string to this

builder.

Appends a string to this string builder.

Deletes characters from startIndex to endIndex.

Deletes a character at the specified index.

Inserts data into this builder at the position offset.

Inserts a value converted to a string into this builder.

Inserts a string into this builder at the position offset.

Replaces the characters in this builder from startIndex to endIndex with the specified string.

Reverses the characters in the builder.

Sets a new character at the specified index in this builder.

Page 39: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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ExamplesstringBuilder.append("Java");stringBuilder.insert(11, "HTML and ");stringBuilder.delete(8, 11) changes the builder to Welcome Java.stringBuilder.deleteCharAt(8) changes the builder to Welcome o Java.stringBuilder.reverse() changes the builder to avaJ ot emocleW.stringBuilder.replace(11, 15, "HTML") changes the builder to Welcome to HTML.stringBuilder.setCharAt(0, 'w') sets the builder to welcome to Java.

Page 40: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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Problem: Checking Palindromes Ignoring Non-alphanumeric Characters

This example gives a program that counts the number of occurrence of each letter in a string. Assume the letters are not case-sensitive.

PalindromeIgnoreNonAlphanumeric PalindromeIgnoreNonAlphanumeric RunRun

Page 41: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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Main Method Is Just a Regular Method

public class A { public static void main(String[] args) { String[] strings = {"New York", "Boston", "Atlanta"}; B.main(strings); } }

class B { public static void main(String[] args) { for (int i = 0; i < args.length; i++) System.out.println(args[i]); } }

You can call a regular method by passing actual parameters. Can you pass arguments to main? Of course, yes. For example, the main method in class B is invoked by a method in A, as shown below:

Page 42: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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Command-Line Parameters

class TestMain {

public static void main(String[] args) {

...

}

}

java TestMain arg0 arg1 arg2 ... argn

Page 43: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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ProcessingCommand-Line Parameters

In the main method, get the arguments from args[0], args[1], ..., args[n], which corresponds to arg0, arg1, ..., argn in the command line.

Page 44: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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Problem: Calculator

Objective: Write a program that will perform binary operations on integers. The program receives three parameters: an operator and two integers.

CalculatorCalculator

java Calculator 2 + 3

java Calculator 2 - 3

RunRun java Calculator 2 / 3

java Calculator 2 “*” 3

Page 45: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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The File ClassThe File class is intended to provide an abstraction that deals with most of the machine-dependent complexities of files and path names in a machine-independent fashion. The filename is a string. The File class is a wrapper class for the file name and its directory path.

Page 46: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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java.io.File

+File(pathname: String)

+File(parent: String, child: String)

+File(parent: File, child: String)

+exists(): boolean

+canRead(): boolean

+canWrite(): boolean

+isDirectory(): boolean

+isFile(): boolean

+getAbsolutePath(): String

+getName(): String

+getPath(): String

+delete(): boolean

+renameTo(dest: File): boolean

Creates a File object for the specified pathname. The pathname may be a directory or a file.

Creates a File object for the child under the directory parent. child may be a filename or a subdirectory.

Creates a File object for the child under the directory parent. parent is a File object. In the preceding constructor, the parent is a string.

Returns true if the file or the directory represented by the File object exists.

Returns true if the file represented by the File object exists and can be read.

Returns true if the file represented by the File object exists and can be written.

Returns true if the File object represents a directory.

Returns true if the File object represents a file.

Returns the complete absolute file or directory name represented by the File object.

Returns the last name of the complete directory and file name represented by the File object. For example, new File("c:\\book\\test.dat").getName() returns test.dat.

Returns the complete directory and file name represented by the File object. For example, new File("c:\\book\\test.dat").getPath() returns c:\book\test.dat.

Deletes this file. The method returns true if the deletion succeeds.

Renames this file. The method returns true if the operation succeeds.

Obtaining file properties and manipulating file

Page 47: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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Problem: Explore File Properties

TestFileClassTestFileClass RunRun

Objective: Write a program that demonstrates how to create files in a platform-independent way and use the methods in the File class to obtain their properties. Figure 16.1 shows a sample run of the program on Windows, and Figure 16.2 a sample run on Unix.

Page 48: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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Text I/O

A File object encapsulates the properties of a file or a path, but does not contain the methods for reading/writing data from/to a file. In order to perform I/O, you need to create objects using appropriate Java I/O classes. The objects contain the methods for reading/writing data from/to a file. This section introduces how to read/write strings and numeric values from/to a text file using the Scanner and PrintWriter classes.

Page 49: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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Writing Data Using PrintWriter

WriteDataWriteData RunRun

java.io.PrintWriter

+PrintWriter(filename: String)

+print(s: String): void

+print(c: char): void

+print(cArray: char[]): void

+print(i: int): void

+print(l: long): void

+print(f: float): void

+print(d: double): void

+print(b: boolean): void

Also contains the overloaded println methods.

Also contains the overloaded printf methods.

.

Creates a PrintWriter for the specified file.

Writes a string.

Writes a character.

Writes an array of character.

Writes an int value.

Writes a long value.

Writes a float value.

Writes a double value.

Writes a boolean value.

A println method acts like a print method; additionally it prints a line separator. The line separator string is defined by the system. It is \r\n on Windows and \n on Unix.

The printf method was introduced in §3.6, “Formatting Console Output and Strings.”

Page 50: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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Reading Data Using Scanner

java.util.Scanner

+Scanner(source: File)

+Scanner(source: String)

+close()

+hasNext(): boolean

+next(): String

+nextByte(): byte

+nextShort(): short

+nextInt(): int

+nextLong(): long

+nextFloat(): float

+nextDouble(): double

+useDelimiter(pattern: String): Scanner

Creates a Scanner that produces values scanned from the specified file.

Creates a Scanner that produces values scanned from the specified string.

Closes this scanner.

Returns true if this scanner has another token in its input.

Returns next token as a string.

Returns next token as a byte.

Returns next token as a short.

Returns next token as an int.

Returns next token as a long.

Returns next token as a float.

Returns next token as a double.

Sets this scanner’s delimiting pattern.

ReadDataReadData RunRun

Page 51: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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Problem: Replacing Text

Write a class named ReplaceText that replaces a string in a text file with a new string. The filename and strings are passed as command-line arguments as follows:

java ReplaceText sourceFile targetFile oldString newString

For example, invokingjava ReplaceText FormatString.java t.txt StringBuilder StringBuffer

replaces all the occurrences of StringBuilder by StringBuffer in FormatString.java and saves the new file in t.txt.

ReplaceTextReplaceText RunRun

Page 52: 1 Strings and Text I/O. 2 Motivations Often you encounter the problems that involve string processing and file input and output. Suppose you need to write.

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(GUI) File Dialogs

ReadFileUsingJFileChooserReadFileUsingJFileChooser RunRun


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