String Builder & String Buffer (Java Programming)
- 1. STRING BUILDER & STRING BUFFER Java Programming Anwar Hasan Shuvo Daffodil International University 1
- 2. Introduction Before getting into this topic we should learn somethings which are really needed.So we will learn about Heap and Stack. Concept of Heap and Stack is very important in this topics. We are going to learn about String, StringBuffer & StringBuilder class. We are starting our presentation with the concept of Heap and Stack 2
- 3. Heap & Stack Basically objects are stored in heap and local variables, methods are stored in stack 3 Heap Objects Stack Local variables & Primitive Datatypes
- 4. String String is immutable object . (immutable means once created can not be changed ) The object created as a String is stored in the Constant String Pool. Every immutable object in Java is thread safe ,that implies String is also thread safe . String can not be used by two threads simultaneously. String once assigned can not be changed. String a = " Hello World " ; // The above object is stored in constant string pool and its value can not be modified a += “Java Programming" ; “Java Programming" string is created in constant pool and referenced by the variable named a. “Hello World" string still exists in string constant pool and its value is not overrided but we lost reference to the “Hello World“ String. 4
- 5. Example with CODE Heap Hello World Java Programming Hello World Heap Hello World 5
- 6. Example with CODE 6 :String Life is a tale told by an idiot :String Shakespeare Life is a tale told by an idiot It can no longer be accessed
- 7. String Buffer StringBuffer is mutable. ( mutable means one can change the value of the object) The object created through StringBuffer is stored in the heap . StringBuffer has the same methods as the StringBuilder , but each method in StringBuffer is synchronized that is StringBuffer is thread safe . Due to this it does not allow two threads to simultaneously access the same method . Each method can be accessed by one thread at a time . But being thread safe has disadvantages too as the performance of the StringBuffer hits due to thread safe property . Thus StringBuilder is faster than the StringBuffer when calling the same methods of each class. StringBuffer value can be changed , it means it can be assigned to the new value . String Buffer can be converted to the string by using toString() method. 7
- 8. EXAMPLE StringBuffer s = new StringBuffer("Hello World") ; // The above object stored in heap and its value can be changed . s.append(“ Java Programming"); // Above statement is right as it modifies the value which is allowed in the StringBuffer 8
- 9. Example with CODE Heap Hello World Heap Hello World Java Programming 9
- 10. String Builder StringBuilder is same as the StringBuffer , that is it stores the object in heap and it can also be modified . The main difference between the StringBuffer and StringBuilder is that StringBuilder is also not thread safe. StringBuilder is fast as it is not thread safe . StringBuilder object= new StringBuilder("Hello"); // The above object too is stored in the heap and its value can be modified object=new StringBuilder("Bye"); // Above statement is right as it modifies the value which is allowed in the StringBuilder 10
- 11. Overview String StringBuffer StringBuilder Storage Area Constant String Pool Heap Heap Thread Safe Yes Yes No Modifiable immutable mutable mutable 11
- 12. Concatenation Of String String can be concatenated by using “+” operator or .concat() method. StringBuffer can be concatenated by using append(). While concatenating StringBuffer is faster than String. Because String is converted into StringBuffer and then it use append() method to concatenate. After that it use toString() method to be converted into String. StringBuffer uses append() method to concatenate. 12
- 13. Process of Concatenation of String And StringBuffer 13 String StringBuffer append() toString String StringBuffer append() toString String StringBuffer