This document contains summaries of various Java concepts: - It defines objects as instances of classes, and describes objects as having state and behavior. - It lists various operator types in Java like arithmetic, relational, assignment, and logical operators, and their precedence. - It provides examples of String methods like length(), charAt(), concat(), and substring(). - It describes the three types of for loops in Java: simple for loop, for-each loop, and variations of if/else and switch statements.

3. • History Of Java
• Features of Java
• Java Architecture
• JVM, JRE, JDK

18. How are Objects created ?
An object is an instance of a class. A class is a
template or blueprint from which objects are created.
So, an object is the instance(result) of a class
Object Definitions:
• An object is a real-world entity.
• An object is a runtime entity.
• The object is an entity which has state and behavior.
• The object is an instance of a class.

24. Operator Type Category Precedence
Unary postfix expr++ expr--
prefix ++expr --expr +expr -expr ~ !
Arithmetic multiplicative * / %
additive + -
Shift shift << >> >>>
Relational comparison < > <= >= instanceof
equality == !=
Bitwise bitwise AND &
bitwise exclusive OR ^
bitwise inclusive OR |
Logical logical AND &&
logical OR ||
Ternary ternary ? :
Assignment assignment = += -= *= /= %= &= ^= |= <<= >>=

25. char[] ch={'j','a','v','a','t','p','o','i','n','t
'};
String s=new String(ch);
String s="javatpoint";
Same
as
length() charAt(int index) contains(CharSeque
nce s)
concat(String str) replace(char old,
char new)
substring(int
beginIndex)
substring(int
beginIndex, int
endIndex)
equals(Object
another)
toLowerCase() toUpperCase()
equalsIgnoreCase(
String another)
split(String regex) indexOf(String ch) trim() valueOf(int value)

26. append(String s) insert(int offset,
String s)
replace(int
startIndex, int
endIndex, String str)
delete(int startIndex,
int endIndex)
reverse()
charAt(int index) length() substring(int
beginIndex)
substring(int
beginIndex, int
endIndex)
substring(int
beginIndex, int
endIndex)

27. There are three types of For Loop:
• Simple for Loop
• For-each or Enhanced for Loop

28. 1.Simple if statement
2.if-else statement
3.if-else-if ladder
4.Nested if-statement
if(condition 1) {
statement 1; //executes when condition 1 is true
}
The switch statement contains multiple blocks of code
called cases and a single case is executed based on the
variable which is being switched. The switch statement is easier
to use instead of if-else-if statements. It also enhances the
readability of the program.
Syntax
switch (expression){
case value1:
statement1;
break;
.
.
.
case valueN:
statementN;
break;
default:
default statement;
}

30. Welcome to Java Coding & All the Best