![StringBuffer Class
Java StringBuffer class is used to created mutable
(modifiable) string. The StringBuffer class in java is same as
String class except it is mutable i.e. it can be changed.
class StringDemo{
public static void main(String args[]){
StringBuffer sb=new StringBuffer("Hello ");
sb.append("Java");//now original string is changed
System.out.println(sb);//prints Hello Java
}
}](https://image.slidesharecdn.com/3-datatypesandvariables-190325061807/85/Data-Types-Variables-in-JAVA-14-320.jpg)
![StringBuilder Class
Java StringBuilder class is used to create mutable (modifiable) string.
The Java StringBuilder class is same as StringBuffer class except that it
is non-synchronized.
class A{
public static void main(String args[]){
StringBuilder sb=new StringBuilder("Hello ");
sb.append("Java");//now original string is changed
System.out.println(sb);//prints Hello Java
}
}](https://image.slidesharecdn.com/3-datatypesandvariables-190325061807/85/Data-Types-Variables-in-JAVA-15-320.jpg)
![Array - Syntax
A particular value in an array is referenced using the array
name followed by the index in brackets.
Datatype [ ] variable_name = new datatype[size];
Ex: int [] scores = new int [10];
In JAVA, int is of 4 bytes, total space=4*10=40 bytes.
Space Allocation is based on the datatype used to declare
array.](https://image.slidesharecdn.com/3-datatypesandvariables-190325061807/85/Data-Types-Variables-in-JAVA-19-320.jpg)
![Dot Operator
Dot operator is used to access methods and variables
within classes.
It is represented as . (dot)
Example
class Test
{
public int a;
public display()
{
System.out.println(“Hello”);
}
}
public static void main(String args[])
{
Test t=new Test();
t.a=32; //accessing dot
t.display(); //accessing display
}
}](https://image.slidesharecdn.com/3-datatypesandvariables-190325061807/85/Data-Types-Variables-in-JAVA-21-320.jpg)
Data Types & Variables in JAVA
- 2. What are DataTypes? Data-types means containers. They specify what kind of data to hold In java, there are two types of data types Primitive data types Non-primitive data types
- 4. Non Primitive Data Types Strings Arrays Class
- 5. Variables Variable is name of reserved area allocated in memory. There are three types of variables in java local variable A variable that is declared inside the method is called local variable. instance variable A variable that is declared inside the class but outside the method is called instance variable . It is not declared as static. static variable A variable that is declared as static is called static variable. It cannot be local.
- 6. Variables Syntax: Datatype variable_name = value ; Example int id = 34; float mks=67.34; int int =45; //invalid
- 7. Literals Literals are numbers, characters, and string representations used in a program. Numeric Literals int roll_no=45; Character literals char letter = ‘b'; letter = ‘S'; String literals String message = "HellotWorldn";
- 8. Casting is required when there is a need to explicitly convert a value from one type to another. The general syntax for a cast is: Examples Casting (result_type) value; float price = 37.53; int dollars = (int) price; // fractional portion lost // dollars = 37 char response = 'A'; byte temp =(byte) response; // temp = 65 (ASCII value // for 'a')
- 9. Type Casting Assigning a value of one type to a variable of another type is known as Type Casting. In Java, type casting is classified into two types, Widening Casting(Implicit) Narrowing Casting(Explicitly done)
- 10. A widening conversion occurs when a value stored in a smaller space is converted to a type of a larger space. There will never be a loss of information Widening conversions occur automatically when needed. Widening Conversions
- 11. A narrowing conversion occurs when a value stored in a larger space is converted to a type of a smaller space. Information may be lost Never occurs automatically. Must be explicitly requested by the programmer using a cast. Narrowing Conversions
- 12. Strings String is a sequence of characters. In the Java programming language, strings are objects. There are two types of String i.e 1. Mutable 2.Immutable In java, string objects are immutable. Immutable simply means unmodifiable or unchangeable. It is immutable because object reference is created.
- 14. StringBuffer Class Java StringBuffer class is used to created mutable (modifiable) string. The StringBuffer class in java is same as String class except it is mutable i.e. it can be changed. class StringDemo{ public static void main(String args[]){ StringBuffer sb=new StringBuffer("Hello "); sb.append("Java");//now original string is changed System.out.println(sb);//prints Hello Java } }
- 15. StringBuilder Class Java StringBuilder class is used to create mutable (modifiable) string. The Java StringBuilder class is same as StringBuffer class except that it is non-synchronized. class A{ public static void main(String args[]){ StringBuilder sb=new StringBuilder("Hello "); sb.append("Java");//now original string is changed System.out.println(sb);//prints Hello Java } }
- 16. Difference between String and StringBuffer String String class is immutable String is slow and consumes more memory String class overrides the equals() method of Object class. StringBuffer StringBuffer class is mutable StringBuffer is fast and consumes less memory StringBuffer class doesn't override the equals() method of Object class
- 17. Difference between String and StringBuffer conti.. StringBuffer StringBuffer is synchronized StringBuffer is less efficient than StringBuilder. StringBuilder StringBuilder is non- synchronized StringBuilder is more efficient than StringBuffer.
- 18. Arrays An array is an ordered list of values 0 1 2 3 4 5 6 7 8 9 79 87 94 82 67 98 87 81 74 91 An array of size N is indexed from zero to N-1 rollno The entire array has a single name Each value has a numeric index This array holds 10 values that are indexed from 0 to 9
- 19. Array - Syntax A particular value in an array is referenced using the array name followed by the index in brackets. Datatype [ ] variable_name = new datatype[size]; Ex: int [] scores = new int [10]; In JAVA, int is of 4 bytes, total space=4*10=40 bytes. Space Allocation is based on the datatype used to declare array.
- 20. Types of Array Single Dimensional Array (1 D Array) Two Dimensional Array (2 D Array) Multidimensional Array(Arrays of Arrays)
- 21. Dot Operator Dot operator is used to access methods and variables within classes. It is represented as . (dot) Example class Test { public int a; public display() { System.out.println(“Hello”); } } public static void main(String args[]) { Test t=new Test(); t.a=32; //accessing dot t.display(); //accessing display } }