1 chapter 2: elementary programming shahriar hossain
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Chapter 2: Elementary Programming
Shahriar Hossain
Quiz solution
What will be the value of the variable x after performing the following Java statement:int x = 7 − 10 % 2 / 3;
Solution: 7
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Consecutive multiplicative operators will be evaluated from left to right in the expression since they have the same priority.
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Quiz solution
What will be printed as a result of the following piece of code? explain step-by-step:double x = 3;
double y = x + 1;
x = y − 2;
System.out.println(x);
System.out.println(y);
Solution:
2.0
4.0
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Objectives To use augmented assignment operators To distinguish between postincrement and
preincrement and between postdecrement and predecrement
To cast the value of one type to another type To represent characters using the char type To represent a string using the String type
To become familiar with Java programming style and documentation
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Declaring Variablesint x; // Declare x to be an // integer variable;
double radius; // Declare radius to // be a double variable;
char a; // Declare a to be a // character variable;
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Assignment Statements
x = 1; // Assign 1 to x;
radius = 1.0; // Assign 1.0 to radius;
a = 'A'; // Assign 'A' to a;
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Numeric Operators
Name Meaning Example Result
+ Addition 34 + 1 35 - Subtraction 34.0 – 0.1 33.9 * Multiplication 300 * 30 9000 / Division 1.0 / 2.0 0.5 % Remainder 20 % 3 2
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Augmented Assignment Operators
Operator Example Equivalent
+= i += 8 i = i + 8
-= f -= 8.0 f = f - 8.0
*= i *= 8 i = i * 8
/= i /= 8 i = i / 8
%= i %= 8 i = i % 8
The operators +, -, *, /, and % can be combined with the assignment operator to form augmented operators.
Caution
There is no spaces in the augmented assignment operators+ = is wrong
+= is correct
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Increment andDecrement Operators
Operator Name Description++var preincrement The expression (++var) increments var by 1
and evaluates to the new value in var after the increment.
var++ postincrement The expression (var++) evaluates to the original value
in var and increments var by 1. --var predecrement The expression (--var) decrements var by 1
and evaluates to the new value in var after the decrement.
var-- postdecrement The expression (var--) evaluates to the original value
in var and decrements var by 1.
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Increment andDecrement Operators, cont.
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Increment andDecrement Operators, cont.
Using increment and decrement operators makes expressions short, but it also makes them complex and difficult to read. Avoid using these operators in expressions that modify multiple variables, or the same variable for multiple times such as this: int k = ++i + i.
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Increment andDecrement Operators, cont.
What is the output of the following code segment?
int i=2;int k=++i+i;System.out.println(i);System.out.println(k);
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Increment andDecrement Operators, cont.
What is the output of the following code segment?
int i=2;int k=i+++i; // equivalent to int k=(i++)+i;System.out.println(i);System.out.println(k);
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Numeric Type Conversion
Consider the following statements:
byte i = 100;
long k = i * 3 + 4;
double d = i * 3.1 + k / 2;
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Conversion RulesWhen performing a binary operation involving two operands of different types, Java automatically converts the operand based on the following rules:
1. If one of the operands is double, the other is
converted into double.2. Otherwise, if one of the operands is float, the other is
converted into float.3. Otherwise, if one of the operands is long, the other is
converted into long.4. Otherwise, both operands are converted into int.
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Type CastingImplicit casting double d = 3; (type widening)
Explicit casting int i = (int)3.0; (type narrowing) int i = (int)3.9; (Fraction part is truncated)
What is wrong? int x = 5 / 2.0;The correct statement is int i=(int)(5/2.0);
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Type Casting
byte, short, int, long, float, double
range increases
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Casting in an Augmented Expression
In Java, an augmented expression of the form x1 op= x2 is implemented as x1 = (T)(x1 op x2), where T is the type for x1. Therefore, the following code is correct.
int sum = 0;
sum += 4.5; // sum becomes 4 after this statement
sum += 4.5 is equivalent to sum = (int)(sum + 4.5).
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Character Data Type
char letter = 'A'; (ASCII)
char numChar = '4'; (ASCII)
char letter = '\u0041'; (Unicode)
char numChar = '\u0034'; (Unicode)
Four hexadecimal digits.
NOTE: The increment and decrement operators can also be used on char variables to get the next or preceding Unicode character. For example, the following statements display character b.
char ch = 'a';
System.out.println(++ch);
ASCII (The American Standard Code for Information Interchange)
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Unicode
An encoding scheme established by the Unicode Consortium
Originally 16-bit but there are supplementary characters beyond the 16-bit limit
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Escape Sequences for Special Characters
Description Escape Sequence Unicode
Backspace \b \u0008
Tab \t \u0009
Linefeed \n \u000A
Carriage return \r \u000D
Backslash \\ \u005C
Single Quote \' \u0027
Double Quote \" \u0022
Example
Is this a correct statement?System.out.println("He said "Java is fun" ");
No. The statement above will give a compiler error
The correct statement will beSystem.out.println("He said \"Java is fun\" ");
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