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Chapter 2: Java
Fundamentals
Type conversion ,String
Chapter Objectives
 Type Conversion
 String Class
 Commonly Used String Methods
 Parsing Numeric Strings
 Commonly Used Escape Sequences
Variables – Cont.
 Float
 The default type of floating point numbers is double .
 The declaration :
float rate = 15.5f ;
without the f , the compiler will generate an error
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Variables – Cont.
 Char
 When using the char data type, you enclose each character
represented within single quotations marks.
 Ex:
char c = ‘A’
char x = ‘&’
char space = ‘ ‘
 Each character is represented by a value (‘A’ is represented by the
value 65)
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Type Conversion (Casting)
 Used:
• to change one data type to another .
• to avoid implicit type coercion.
 Syntax:
(dataTypeName) expression
 Expression evaluated first, then the value is converted to
dataTypeName
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Type Conversion (Casting)

Examples:
1. (int)(7.9 + 6.7) = 14
2. (int)(7.9) + (int)(6.7) = 13
3. (double)(17) = 17.0
4. (double)(8+3) = (double)11 = 11.0
5. (double)(7) /2 = 7.0/2 = 3.5
6. (double)(7/2) = 3.0
7. (int)(7.8+(double)(15)/2) =
(int)15.3 =15
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Type Conversion (Casting)
8. (int)(‘A’)
9. (int)(‘8’)
10. (char)(65)
11. (char)(56)
= 65
= 56
= ‘A’
= ‘8’
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The class String
 Contains operations to manipulate strings.
 String:
 Sequence of zero or more characters.
 Enclosed in double quotation marks.
 Is processed as a single unit .
 Null or empty strings have no characters. “ “
 Every character has a relative position , the first character is in
position 0 .
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The class String
 Java system automatically makes the class String available (i.e
no need to import this class )
 Example :
Consider the following declaration :
String sentence ;
sentence = “programming with java”
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The class String
 Length of the string is the number of characters in
it .
 When determining the length of a string , blanks
count .
 Example :
 “ “  has length = 0
 “abc”  has length = 3 , position of a = 0 ,b= 1 , c= 2
 “a boy”  has length = 5
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Some Commonly Used String
Methods
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Some Commonly Used String
Methods
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Some Commonly Used String
Methods
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Some Commonly Used String
Methods
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Examples on string methods
String s1 , s2 , s3 ;
s1 = “abcdefeg” ;
System.out.println( s1.length() ); // 8
System.out.println(s1.charAt(3)); //d
System.out.println(s1.indexOf(‘e’)); //4
System.out.println(s1.indexOf(“cd”)); //2
System.out.println(s1.toUpperCase()); //ABCDEFEG
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Examples on string methods
System.out.println(s1.substring(1 , 4)); //bcd
System.out.println(s1 + “xyz”); // abcdefegxyz
System.out.println( s1.replace(‘d’ ,’D’)); // abcDefeg
System.out.println(s1.charAt(4) ); // e
System.out.println(s1.indexOf(‘b’)); // 1
System.out.println(s1.indexOf(‘e’,5)); // 6
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Input
 Reading a Single Character
if ch is a char variable. To input A into ch, you can use the
following statement:
ch = console.next().charAt(0);
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Parsing Numeric Strings


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
Integer, Float, and Double are classes designed to
convert a numeric string into a number.
These classes are called wrapper classes.
parseInt is a method of the class Integer, which
converts a numeric integer string into a value of the type
int.
parseFloat is a method of the class Float and is used
to convert a numeric decimal string into an equivalent value
of the type float.
parseDouble is a method of the class Double, which
is used to convert a numeric decimal string into an equivalent
value of the type double.
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Parsing Numeric Strings

A string consisting of only integers or decimal numbers is
called a numeric string.

To convert a string consisting of an integer to a value of the
type int, we use the following expression:
Integer.parseInt(strExpression)
• Example:
Integer.parseInt("6723") = 6723
Integer.parseInt("-823") = -823
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Parsing Numeric Strings

•
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•
To convert a string consisting of a decimal number to a value of the type
float, we use the following expression:
Float.parseFloat(strExpression)
Example:
Float.parseFloat("34.56") = 34.56
Float.parseFloat("-542.97") = -542.97
To convert a string consisting of a decimal number to a value of the type
double, we use the following expression:
Double.parseDouble(strExpression)
Example:
Double.parseDouble("345.78") = 345.78
Double.parseDouble("-782.873") = -782.873
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Formatting Output with
printf
 The syntax to use the method printf to produce output on
the standard output device is:
System.out.printf(formatString);
or
System.out.printf(formatString,argumentList)
;
 formatString is a string specifying the format of the
output and argumentList is a list of arguments.
 argumentList is a list of arguments that consists of
constant values, variables, or expressions.
 If there is more than one argument in argumentList, the
arguments are separated with commas.
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Formatting Output with
printf
System.out.printf("Hello there!");
Consists of only the format string and the statement:
System.out.printf("There are %.2f inches in %d
centimeters.%n",
centimeters / 2.54, centimeters);
 Consists of both the format string and argumentList.
 %.2f and %d are called format specifiers.
 By default, there is a one-to-one correspondence between format
specifiers and the arguments in argumentList.
 The first format specifier, %.2f, is matched with the first argument,
which is the expression centimeters / 2.54.
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Formatting Output with printf
 The second format specifier, %d, is matched with the
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second argument, which is centimeters.
The format specifier %n positions the insertion point at the
beginning of the next line.
If centimeters = 150  150/2.54 =59.05511811023
The o/p would be :
There are 59.06 inches in 150 centimeters
The output of a printf statement is right-justified by default.
To force the output to be left-justified, negative column
widths may be used.
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Example1
public class Example3_6
{
public static void main (String[] args)
{
int num = 763;
double x = 658.75;
String str = "Java Program.";
System.out.println("123456789012345678901234567890");
System.out.printf ( "%5d%7.2f%15s%n", num, x, str);
System.out.printf ("%15s%6d%9.2f %n", str, num, x);
}
}
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Example1
Sample run :
123456789012345678901234567890
763 658.75 Java Program.
Java Program. 763 658.75
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Example2
public class Example3_7
{
public static void main (String[] args)
{
int num = 763;
double x = 658.75;
String str = "Java Program.";
System.out.println("123456789012345678901234567890");
System.out.printf("%-5d%-7.2f%-15s ***%n", num, x, str);
System.out.printf("%-15s%-6d%- 9.2f ***%n", str, num, x);
}
}
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Example2
Sample Run :
123456789012345678901234567890
763 658.75 Java Program. ***
Java Program. 763 658.75 ***
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Formatting Output with
printf
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Commonly Used
Escape Sequences
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