1.
JAVA Character Set
Character set is a set of valid characters that a language can recognise.
A Character represents any letter, digit or any other sign.
Java uses the Unicode character set.
Unicode is a two-byte character code set that has characters
representing almost all characters in almost all language and writing
Systems around all the world including English, Arabic, Chinese etc.
2.
Token
The smallest individual unit in a program is known as Token.
In a Java program, all characters are grouped into symbols called tokens.
Java has the following types of tokens: keyword , Identifier, literal, punctuators,operators.
lower-case <= a|b|c|d|e|f|g|h|i|j|k|l|m|n|o|p|q|r|s|t|u|v|w|x|y|z
upper-case <= A|B|C|D|E|F|G|H|I|J|K|L|M|N|O|P|Q|R|S|T|U|V|W|X|Y|Z
alphabetic <= lower-case | upper-case
numeric
<= 0|1|2|3|4|5|6|7|8|9
alphanumeric <= alphabetic | numeric
special
<= !|%|^|&|*|(|)|-|+|=|{|}|||~|[|]||;|'|:|"|<|>|?|,|.|/|#|@|`|_
graphic
<= alphanumeric | special
3.
Keywords
Keywords are words that have a specific predefined meaning in Java.
They cannot be used as variable names.
These are reserved for special purpose. They are also known as reserve words.
abstract
assert
boolean
break
byte
case
catch
char
class
const
continue goto
package switch
default if
private this
do
implements
protected
throw
double import public throws
else
instanceof
return transient
extends int
short
try
final
interface static
void
finally long
strictfp volatile
float
native super
while
for
new
synchronized
4.
Identifiers :
Identifiers are fundamental building blocks of a program and are used as the
General terminology for the names given to differnent parts of the program i.e.
Variables, objects, classes, functions, arrays, packages etc.
Identifiers forming rules of java state the following
1. Identifier can have alphabets, digits and underscore and doller sign characters.
2. They must not be a keyboard or boolean literal or null literal.
3. They must not begin with a digit.
4. They can be of any length.
5. Java is case sensitive.
5.
Literals:
Items having fixed data values are referred to as Literals.
They are also known as Constants.
Various types of literals available in Java are :
Integer literals
Floating literals
Boolean literals
Character literals
String literals
Null literals
6.
Literals
Literals (often referred to as constants) are data items that never change their value
during a program run.
JAVA allows several kinds of literals:
1. Integer Constant
2. Floating Constant
3. Character Constant
4. String Constant
Literals
7.
Integer Constants
Integer constants are whole numbers without any fractional part. The method of writing
integer constants has been specified in the following rule:
An integer constant must have at least one digit and must not contain any decimal
point. It may contain either + or - sign. A number with no sign is assumed to be
positive. Commas cannot appear in an integer constant.
8.
JAVA allows three types of integer constants:
1. Decimal (base 10)
2. Octal (base 8)
3. Hexadecimal (base 16)
1. Decimal Integer Constants. An integer constant consisting of a sequence of
digits is taken to be decimal integer constant unless it begins with a (digit zero).
For instance, 1234,41, + 97, -17 are decimal
integer constants.
2. Octal Integer Constants. A sequence of digits starting with 0 (digit zero) is taken
to be an octal integer. For instance, decimal integer 8 will be written as 010 as
octal integer. and decimal integer 12 will be written as 014 as octal integer
3. Hexadecimal Integer Constants. A sequence of digits preceded by Ox or OX is
taken to be an hexadecimal integer. For instance, decimal 12 will be written as oxe
as hexadecimal integer. Thus number 12 will be written either as 12 (as
decimal), 014 (as octal) and oxe (as hexadecimal).
The suffix I or Land u or U attached to any constant forces it to be represented as
a long and unsigned respectively.
9.
Character Constants
A character constant is one character enclosed in single quotes. The rule for
writing character constant is given below:
A character constant in JAVA must contain one character and must be
enclosed in single quotation marks.
JAVA allows you to have certain nongraphic characters in character constants.
Nongraphic characters are those characters that cannot be typed directly from
keyboard e.g., backspace, tabs, carriage return etc.
These nongraphic characters can be represented by using escape sequences.
An escape sequence is represented by a backslash () followed by one or more
characters.
10.
Following table gives a listing of escape sequences:
a
b
f
n
r
t
v
'
"
?
On
xHn
o
Audible bell (alert)
Backspace
Formfeed
Newline or !inefeed
Carriage Return
Horizontal tab
Vertical tab
Backslash
Single quote
Double quote
Question mark
Octal number (On represents the number in octal)
Hexadecimal number (Hn represents the number in hexadecimal)
Null
11.
Floating Constants
Floating constants are also called real
constants.
Real constants are numbers having fractional parts. These may be written in one of the two
forms called fractional form or the exponent form.
A real constant in fraction form consists of signed or unsigned digits including a decimal
point between digits. The rule for writing a real constant in fractional form is given below:
note :-
A real constant in fractional form must have at least one digit before a
decimal point and at least one digit after the decimal point. It may also have either +
or - sign preceding it. A real constant with no sign is assumed to be positive.
The following are valid real constants in fractional form :
2.0, 17.5, - 13.0, - 0.00625
The following are invalid real constants :
7
(No decimal point)
7.
(No digit after decimal point)
+ 17/2
(I-illegal symbol)
17,250.26.2 (Two decimal points)
17,250.262 (comma not allowed)
12.
A real constant in exponent form consists of two parts: mantissa and exponent.
For instance, 5.8 can be written as 0.58 x 101 =0.58 an where mantissa part is 0.58
(the part appearing before E) and exponent part is 1 (the part appearing after E). E01
represents ~01. The rule for writing a real constant in exponent formis given below:
A real constant in exponent form has two parts: a mantissa and an exponent.
The mantissa must be either an integer or a proper real constant. The mantissa is
followed by a letter E or e and the exponent. The exponent must be an integer.
The following are the valid real constants in exponent form :
152E05, 1.52E07, 0.152E08, 152.0E08, 152E+8, 1520E04, -O.172E3
The following are invalid real constants in exponent form:
(i) 172.E5
(ii) 1.7E
(At least a digit must follow the decimal point)
(No digit specified for exponent)
(iii) 0.17E2.3
(Exponent can not have fractional part)
(iv) 17,225E02
(No comma allowed)
(v) .25E-7
(No preceding digits before decimal point)
13.
terminator character
String Literals
'Multiple Character' constants are treated as string-literals. The rule for writing
string-literal is given below :
A string literal is a sequence of characters surrounded by double quotes
Each character may be represented by an escape sequence.
A string literal is of class type String. And each character takes 2 bytes.
For instance,
"abc" size is 6 bytes.
“ab”
14.
Null Literal :
The null type has one value, the null reference represented by the literal null,
Which is formed from ASCII characters.
A null literal is always of the null type.
Separators :
The following nine ASCII character are the separators (punctuators)
() {} [] ;
,
.
15.
Operators:
Operators are special symbols that perform specific operations on
one, two, or three operands, and then return a result.
Operators Precedence
postfix expr++ expr
unary ++exprexpr+exprexpr~ !
multiplicative * / %
additive + shift <<>>>>>
relational <><= >= instanceof
equality == !=
bitwise AND &
bitwise exclusive OR ^
bitwise inclusive OR |
logical AND &&
logical OR ||
ternary ? :
assignment = += =*= /= %= &= ^= |= <<= >>= >>>=
16.
Data Types
To Identify the type of data and associated operations of handling it.
Java data types are of two types
1) Primitive data types 2) Reference Data Types
17.
Primitive Data Types:
A primitive type is predefined by the language and is named by a reserved keyword.
Thus by primitive data types, we mean fundamental data types offered by JAVA.
The eight primitive data types supported by the Java programming language are:
byte: The byte data type is an 8bit signed two's complement integer. It has a
minimum value of -128 and a maximum value of +127 (inclusive).
short: The short data type is a 16bit signed two's complement integer. It has a
minimum value of -32,768and a maximum value of +32,767 (inclusive).
int: The int data type is a 32bitsigned two's complement integer. It has a
minimum value of2,147,483,648and a maximum value of 2,147,483,647 (inclusive).
long: The long data type is a 64bitsigned two's complement integer. It has a
minimum value of 9,223,372,036,854,775,808and a maximum value of
9,223,372,036,854,775,807(inclusive).
18.
float: The float data type is a singleprecision32bitIEEE 754 floating point.
double: The double data type is a doubleprecision64bitIEEE 754 floating point.
boolean: The boolean data type has only two possible values: true and false.
Use this data typefor simple flags that track true/false conditions.
char: The char data type is a single 16bitUnicode character. It has a minimum
value of'u0000' (or 0) and a maximum value of 'uffff ' (or 65,535 inclusive).
Boolean Type :- Boolean data type used to represent a single ture/false value.
a Boolean value can have only one of two values : True or False.
Value
Datatype
Value
178
26.34e2
87.363F
37.266
8864L
37.266D
True
26.77e3
‘c’
false
Datatype
19.
Reference Data Types :
Reference data types store the memory address of an object.
Class, Interface and Array are the example of Interface Reference Data types.
A reference is called a pointer or a memory address in other language.
An importance reference type that you are use in JAVA is String type.
The String data type lets you create variables that can hold textual data.
“RAM”, “House_No_68”, “500”, AB56”
20.
Variables :
Variable is a named storage locations, which holds a data value of a particular data
Type. And whose value can be manipulated during program run.
Declaration of a variable
The Syntax is
type variable_name;
Example
int age;
double amount;
float marks;
When a more than one identifier of a same type
double salary,wage;
int month,day,year;
Long dis,area;
21.
Initialization of Variables :
int salary;
A simple definition does not provide a first value or initial value to the variable i.e.
Variable is uninitialized and the variable’s value is said to be undefined.
A variable with a declared first value is said to be initialised variable.
int salary=30000;
double price=200.50, discount=0.10;
float a=0.20f;
Dynamic initialization
A call to a method, in which case the return value determines the initialization.
For example
int a=10,b=4;
int c=Math.sqrt(a*a + b*b);
System.out.println(“The Result is “ +c);
Default initial value of variables
22.
TEXT Interaction in GUI
There are four types of methods
1) getText() 2) parse …..() , 3) setText() 4) JOptionPane.showMessageDialog()
1 ) getText() Method :- Obtaining text from a GUI Component
A getText() method returns the text currently stored in a text based GUI component.
The Swing components that support getText() method include : Text Field, Text Area,
Button, Label,Check Box and Radio Button.
To obtain text from nameTextField, you need to write : nameTextField.getText();
Complete statement to obtain text from nameTextField store in a variable :
23.
Parse …. () Methods – Obtaining numbers from a GUI component
Sometimes, you use text type components in a GUI but you intend to use it for
Obtaining numeric values e.g. you may want to read age of a person through a text
Field.
So you need a method that helps you convert this textual data into a numeric type.
There are many parse…..() methods that help you parse string into different numeric
Types.
1)
2)
3)
4)
5)
6)
Byte.parseByte(String s);
Short.parseShort(String s);
Integer.parseInt(String s);
Long.parseLong(String s);
Float.parseFloat(String s);
Double.parseDouble(String s);
First , you have to obtain text from nameTextField by typing a statement like
String str=nameTextField.getText();
After that
int a=Integer.parseInt(str);
24.
You can combined code to obtain numeric input from a text field
int a=Integer.parseInt(nameTextField.getText());
System.out.print – NON GUI Output Method
If you write System.out.println(“Hello World”);
If you write
System.out.println(“Hello ”);
System.out.println(“World”);
But if you write
System.out.print(“Hello ”);
System.out.print(“World ”);
25.
setText() Method :- Storing text into a GUI component
A setText() method stores or changes text in a text based GUI component.
The Swing components that support setText() method include : Text Field,
Text Area, Button, Label,Check Box and Radio Button.
If you want to change the nameTextField
nameTextField.setText(“Rajeev Verma”);
String str=“Rajeev Verma”
nameTextField.setText(str);
26.
JOptionPane.showMessageDialog() Method :- Displaying message in a dialog form
You can produce a basic dialog displaying a message to the user.
The user will see your message with only an “OK” button to close the dialog.
To use this method, you need to perform it in two steps :
1) Firstly, in the source editor, where you type your code, at top most position type the
following line.
import javax.swing.JOptionPane;
2) Now display desired message as per following syntax ;
JOptionPane.showMessageDialog(null, “<Desired message here>”);
for example :
27.
Variable Scope :Scope generally refers to the program-region within which a variable is accessible.
The broad rule is : a variable is accessible within the set of braces it is declared in
{
int a;
…….
…………..
}
For example
Public class ex4
{
int x;
x=10;
if(x==10)
{
int y=20;
x=y*2;
}
y=100;
System.out.println(“x is “ +x);
Sytem.out.println(“ y is “ +y);
28.
Constants :
If you do not want to change a value during a program run.
With the final keyword
final double pi=3.14;
Advantages of Constants :
1) They make your program easier to read and check for correctness.
2) If a constant needs to be changed all you need to do is change the declaration.
29.
Operators in JAVA :The operations are represented by operators and the objects of the operations are
referred to as operands.
Unary operators :Operators that act on one operand are referred to as Unary operators.
1. Unary + :- + precedes an operand.
for example if a=5 then +a means +5
if a =-4
1. 2. Unary - :- - precedes an operand.
for example if a=5 then –a means -5
if a =-4
30.
Binary operators :Operators that act upon two operands are referred to as binary operators.
For example :- These operators perform addition, subtraction, multiplication,
and division. These symbols are similar to mathematical symbols.
The only symbol that is different is "%", which divides one operand by another and
returns the remainder as its result.
+ addition operator
- subtraction operator
* multiplication operator
/ division operator
% remainder operator
31.
Operator + with Strings
For example
5+6=11
“5” + “6”=“56”
“abc” + “123” = “abc123”
“ “ +5 + “xyz”= “5xyz”
32.
Increment/Decrement Operators (+ +, --)
JAVA includes two useful operators not generally found in other computer
languages (except C and C++). These are the increment and decrement
operators,
+ + and - -. The C++ name itself is influenced by the increment operator
+ +. The operator + + adds 1 to its operand, and --subtracts one.
33.
However, both the increment and decrement operators come in two
varieties : they may either precede or follow the operand.
The prefix version comes before the operand (as in ++a or --a) and
the postfix version comes after the operand (as in a + + or a --).
The two versions have the same effect upon the operand, but they
differ when they take place in an expression.
34.
Working with prefix version:- When an increment or decrement operator
precedes its operand (i.e., in its prefix form), JAVA performs the increment or
decrement operation before using the value of the operand. For example, the
expression .
The prefix increment or decrement operators follow change-then-use rule
i.e., they first change (increment or decrement) the value of their operand.
then use the new value in evaluating the expression
sum = sum + (+ + count) ;
The expression P = P * --N;
35.
Working with postfix version:- When an increment or decrement operator
follows its operand and (i.e., in its postfix form), C+ + first uses the value of
the operand in evaluating the expression before incrementing or
decrementing the operand's value.
The postfix increment or decrement operators follow use-then-change rule i.e
.• they first use the value of their operand in evaluating the expression , and
then change (increment or decrement) the operand's value.
For example, the exp
sum = sum + count ++;
The expression P = P * N--;
36.
The increment operator + + and decrement operator - - are unary operators
i.e., they operate upon single operand.
37.
Evaluate x = + + Y + 2y if y = 6.
Evaluate b= a + + + + + a if a is 10 initially.
Evaluate z = + +x + x+ + if x = 15 initially.
38.
Relational Operators
In the term relational operator, relational refers to the relationships
that values (or operands) can have with one another.
Thus, the relational operators determine the relation among different
operands.
JAVA provides six relational operators for comparing numbers and
characters, But they don't work with strings.
If the comparison is true, the relational expression results into the value 1
and to 0, if the comparison is false.
39.
The six relational operators are :
< (less than)
<= (less than or equal to)
== (equal to)
> (greater than)
>= (greater than or equal to)
! = (not equal to)
40.
Relational Operators
Symbol
==
Name
comparison (equality)
Example
Result
6==5
o i.e. false
Comment
returns boolean truth value (0 for
false, 1 for true).
<
!=
greater than or equal to
Not equal to
6<=5
0
1
6>5
1
0
6>=5
1
5>6
>=
greater than
1
5>6
>
0
5<=6
less than or equal to
6<5
5<6
<=
less than
0
6!=5
0
5!=6
0
returns boolean truth value.
returns boolean truth value.
returns boolean truth value.
returns boolean truth value.
returns boolean truth value.
41.
The relational operators have a lower precedence than the arithmetic operators.e
Some tips regarding relational operators.
Do not confuse the = and the == operators.
A very common mistake is to use the assignment operators = in place of the
relational operator == . Do not confuse the testing the operator = = with the
assignment operator (=). e
42.
Predict the output of following code segment
int chk = 6 ;
cout « "chk = = 8 is" « chk = = 8 « "n" ;
cout « "chk = 8 is" « chk = 8 « "n" ;
43.
Tip :- Avoid equality comparison on floating-point numbers
Floating-point arithmetic is not as exact and accurate as the integer
arithmetic is. For instance, 3 * 5 is exactly 15, but 3.25 * 5.25 is nearly equal to
17.06 (if we are working with number with 2 decimal places). The exact
number resulting from 3.25 * 5.25 is 17.0625.
44.
Logical Operators
Relational operators that establish relationships among the values. Logical
operators that refer to the ways these relationships (among values) can
be connected.
C++ provides three logical operators to combine existing expressions.
1)
|| (logical OR)
2)
&& (logical AND)
3)
! (logical NOT)
45.
The logical OR operator (||)
The logical OR operator (||) combines two expressions which make its
operands.
The logical OR (||) operator evaluates to true i.e., 1 if either of its operands
evaluate to true.
46.
Following are some examples of logical OR operation:
(4 = = 4) || (5 = = 8)
0 || 0
results into 1 (true) because first expression is true.
results into 0 (false) because neither expression is true
(both are 0 i.e., false).
5>8 || 5<2
results into 0 (false) because both expressions are
false.
0 || 8
results into 1 (true) because second expression is true.
47.
The logical AND operator (&&)
The logical AND operators, written as &&, also combines two expressions
into one. The resulting expression has the value 1 (true) only if both of the
original expressions (its operands) are true.
48.
some examples of AND operator (&&).
(6 = = 3) && (4 = = 4)
results into 0 (false) because first expression is
false.
(4 = = 4) && (8 = = 8)
results into 1 (true) because both expressions
are true.
6<9 && 4>2
results into 1 (true) because both expressions
are true.
6>9 && 5<2
results into 0 (false) because both expressions
are false.
49.
The Logical NOT operator ( ! )
The logical NOT operator, written as !, works on single expression or operand
i,e., it is a unary operator. The logical NOT operator (!) negates or reverses the
truth value of the expression following it i.e., if the expression is true, then !
expression is false, and vice versa.
50.
some examples of logical NOT operation:
! (5)
results into 0 (false) because 5 is non zero (i.e., true)
! (0)
results into 1 (true) because 0 is zero (i.e., false)
! (5 > 2) results into 0 (false) because the expression 5 > 2 is true
i.e., 1.
! (5 > 9) results into 1 (true) because the expression 5 > 9 is false
i.e., O.
51.
Logical Operators
Sym
bol
Name
Example
Result
&&
And
(6<=6)&&(5<3)
0
Comment
returns boolean truth value (0 for false, (1 for
true))
Both expressions must return 1 for && to
return!
II
Or
(6<=6)11(5<3)
1
one of the expressions must return 1 for || to
return
1.
!
Not
! (6 <= 6)
0
! (5 > 9)
1
Negates the result of expression.
52.
JAVA offers special shorthands that simplify the coding of a certain type of
assignment statement.
For example,
a = a + 10 ;
can be written as
a + = 10 ;
The operator pair + = tells the compiler to assign to a the value of a + 10.
This shorthand works for all the binary operators in JAVA (those that require
two operands).
53.
The general form of JAVA shorthand is
var = var operator expression
Is same as
var operator = expression
Following are some examples of C+ + shorthands:
x - = 10 ; equivalent to
x =x – 10 ;
x * = 3;
equivalent to
x=x*3;
x /= 2 ;
equivalent to
x = x/2 ;
x % = z ; equivalent to
x=x%z;
54.
Conditional Operator ? :
JAVA offers a conditional operator (?:) that stores a value depending upon
a condition. operator is ternary operator i.e., it requires three operands. The
general form of conditional operator ?: is as follows:
expression1 ? expression2 : expression3
If expression1 evaluates to true i.e., 1, then the value of the whole expression is the
value expression2,
otherwise, the value of the whole expression is the value of expression3
55.
For Example :result = marks >= 50 ? ' P' : ' F' ;
The identifier result will have value 'P' if the test expression marks >= 50 evaluates
to true (1) otherwise result will have value' F'
A= 4==9 ? 10 : 25
int large = (( a > b ) ? (( a > c ) ? a : c ) : (( b > c ) ? b : c ));
56.
An expression is composed of one or more operations. The objects of the
operation(s) are referred to as operands. The operations are represented by
operators. Therefore, operators, constants, and variables are the constituents
of expressions.
DEF. An expression in JAVA is any valid combination of operators,
constants and variables.
The expressions in JAVA can be of any type: arithmetic expression,
relational (or logical expression, compound expression etc.
57.
Type of operators used in an expression determine the expression type.
For instance, if expression is formed using arithmetic operators, it is an
arithmetic expression; if an expression relational and/or logical operators, it is
a logical expression. An arithmetic expression always results in a number
(integer or real) and a logical expression always results in a logical value either
TRUE (1) or FALSE (0).
58.
Arithmetic Expressions
Arithmetic expressions can either be integer expressions or real expressions.
Sometimes a mixed expression can also be formed which is a mixture of real and
integer expressions.
Integer expressions are formed by connecting integer constants and/or integer
variables using integer arithmetic operators.
The following are valid integer expressions:
const count = 30 ;
int I, J, K, X, Y, Z ;
(a)I
(b) -J
(c) K-X
(d) K + X - Y + count
(e) -J + K * Y
f) J/Z
(g) Z % X
59.
Real expressions are formed by connecting real constants and/or real
variables using real arithmetic operators (e.g., % is not a real arithmetic
operator).
The following are valid real expressions :
canst bal = 250.53 ;
float qty, amount, value; double fin, inter ;
(i) qty/amount
(iii) (amount + qty * value) - bal
(v) inter - (qty * value) + fin
(ii) qty * value
(iv) fin + qty * inter
60.
The process of converting one predefined type into another is called
Type conversion
JAVA facilitates the type conversion in two forms
1. Implicit type conversion
2. Explicit type conversion
61.
(i) Implicit type conversion. An implicit type conversion is a
conversion performed by compiler without programmer's intervention.
An implicit conversion is applied generally whenever differing data
types are intermixed in an expression (mixed mode expression), so as
not to lose information.
The JAVA compiler converts all operands upto the type of the
largest operand, which is type promotion.
62.
This is done operation by operation, as described in the following type
conversion algorithm:
1. Otherwise, if either operand is of type double, the other is converted
to double
2.Otherwise, if either operand is float, the other is converted to float.
3 .Otherwise, the integral promotions are performed on both operands.
63.
(ii) Explicit type conversion. An explicit type conversion is user-defined
that forces an expression to be of specific type.
The explicit conversion of an operand to a specific type is called type
casting.
64.
Type casting in JAVA is done as shown below:
(type) expression
where type is a valid JAVA data type to which the conversion is to be done. For
example, to make sure that the expression (x + y /2) evaluates to type float,
write it as :
(float) (x + y / 2)
65.
Assigning a value to a type with a greater range (e.g., from short to long) poses
no problem, however, assigning a value of larger data type to a smaller data
type (e.g., from double to float) may result in losing some precision.
66.
There are some other similar potential conversion problems that are listed below
Conversion
Potential Problems
Bigger floating-point type to
smaller floating-point type (e.g.,
double to float)
Loss of precision
Floating point type to integer type
Loss of fractional part.
Bigger integer type to smaller
integer type (e.g., long to short)
Original value may be out of range
for target type. Typically, just
resulting in loss of information.
67.
In JAVA, when a mixed expression is evaluated, it is first divided into
component sub-expressions upto the level of two operands and an
operator. Then the type of sub-expression is decided keeping in mind
general conversion rules. Using the results of sub-expressions, the next
higher level of expression is evaluated and its type is determined. This
process is continued till you get the final result of the expression. Example
Evaluate the following JAVA expression:
int a, mb = 2. k = 4 ;
a = mb * 3/4 + k /4 + 8 - mb + 5/ 8;
68.
logical Expressions
The expressions that result into 0 (false) or 1 (true) are called logical
expressions. The logical expressions are combination of constants, variables
and logical and relational operators
The following are examples of some valid logical expressions :
(i)x> y
(ii) (y+ z>=(x/ z)
(iii) (a + b>c && (c + d) > a
(iv) (y >x)|| (z < y)
69.
An expression is composed of one or more operations. An expression
terminated ; semicolon) becomes a statement. Statements form the smallest
executable unit within a JAVA program.
Statements are terminated with a semicolon.
An assignment statement assigns value to a variable. The value assigned
may be a constant, variable or an expression.
The general form of an assignment statement is as follows :
a = eve;
where a is the variable to whom the value is being assigned and
eve can either be a constant or variable or an expression.
70.
Following are some examples of assignment statements:
x = 14;
Y = 3.2;
Z =x + y;
Z = z * x;
A =b + e - d;
The symbol '=' is called the assignment operator.
71.
Block
A Block is a group of zero or more statement between balanced braces and
can be used anywhere a single statement is allowed.
If (Character.isUpperCase(aChar))
{
Block
label1.setText(“The Character “ + aChar + “is upper Case”);
}
else
{
Another
label1.setText(“The Character “ + aChar + “is lower Case”);
Block
label1.setText(“Thank You”);
}
72.
Null or Empty Statement
The Simplest statement of them all is the empty or null statement
It takes in the following statement
;
A null statement is useful in those instances where the syntax of the language
Requires the presence of a statement but the logic of the program does not.
73.
Q.No.1 Given the following code fragment
int ch = 20 ;
System.out.println(++ch);
System.out.println(ch);
i) What output does the above code fragment produce ?
ii) What is the effect of replacing ++ch with ch+1 ?
Q.No.2 What will be the result of following two expression if i = 10 initially ?
I ) ++i <= 10
ii) i++ <= 10
Q.No. 3 Given the two following expressions :
a) val = 3
b) val = = 3
i ) How are these two different ?
Q.No. 4 What output will the following code fragment produce ?
int val, res, n = 1000 ;
res = n + val > 1750 ? 400 : 200 ;
System.out.println(res);
i) if the input is 2000 ii) if the input is 1000 iii) if the input is 500
74.
Q. no. 5Given the following set of identifiers :
byte b ; char ch; short sh; int intval; long longval ; float fl;
Identify the datatype of the following expressions :
a) ‘a’ -3 b) intval * langval - ch c) fl + longval / sh
Q.No. 6 Will the value of y be the same for the two cases given below ?
i) y = ++x ii) y = x++
Q.No.7 Consider the following code snippet
int i = 10 ;
int n = i++ % 5 ;
What are the values of i and n after the code is executed ?
Q.No. 8 Which of the following are valid identifiers why/ why not ?
1) Data_rec , _data, 1 data, data 1, my.file, switch, goto, break
Q.No. 9 What would be the output of the following program ?
int a =1 , b =2, c =4;
a = +c + ++b / c;
jTextField1.setText( “ a = “ +String.valueOf(a));
Q.No. 10 What would be the output of the following program ?
int a,b =30;
a = 30/2 * b;
jTextField1.setText( “ a = “ +String.valueOf(a));
75.
Q. no. 11 What would be the output of the following program ?
float p = 10.45f;
p= p++ + 1;
jTextField1.setText( “ p = “ +String.valueOf(p));
Q. no. 12 What would be the output of the following program ?
int p=10, k=20;
k = k / ++p;
jTextField1.setText( “ k = “ +String.valueOf(k));
Q. no. 13 What would be the output of the following program ?
int z,x=5,y=-10, a=4,b=2;
z= x++ - --y * b/a;
What number will z in the sample code above contain ?
a) 5
b) 6
c) 10
d) 11
e) 12
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