In computer programming, a string is traditionally a sequence of characters, either as a literal constant or as some kind of variable.
A Java string is therefore a series of characters collected together, like the word "Java", or the phrase "practice makes perfect". Create a string in the code by writing its chars out between double quotes. String str = "Java"; This picture shows the string object in memory, made up of the individual chars J a v a.
Java String is class that java vendors have written and put into java API . It is present in java.lang package.best core java training in bangalore It is a immutable class,means once we created its object we can not modify that,if we will try to modify new object will be created.
Why string is immutable?
Performance: By making Strings immutable it is possible to cache them more aggressively
Security: Parameters are typically represented as string in network connections, database connection urls, usernames/passwords etc. If it were mutable, these parameters could be easily changed.
Synchronization and concurrency: It make String immutable automatically makes them thread safe thereby solving the synchronization issues.
Caching: When compiler optimizes String objects, it sees that if two objects have same value (a="test", and b="test") and thus you need only one string object (for both a and b, these two will point to the same object).java/j2ee classes bangalore
Class loading: String is used as arguments for class loading. If mutable, it could result in wrong class being loaded (because mutable objects change their state).
How string is immutable?
Strings are considered immutable in Java because when we assign new value to a string then the new value is not allocated at the same address space in memory where the older value was stored.
Instead, the old value is discarded and the space it took in the memory is cleaned up by the JVM's garbage collector and new space is allocated in the memory where new value of the string is stored.
JDK provides two classes to support mutable strings: StringBuffer and StringBuilder.java course in bangalore
A StringBuffer or StringBuilder object is just like any ordinary object, which are stored in the heap.
StringBuffer class is used to create a mutable string object. It represents growable and writable character sequence. As we know that String objects are immutable, so if we do a lot of changes with String objects, we will end up with a lot of memory leak. So StringBuffer class is used when we have to make lot of modifications to our string. It is also thread safe i.e multiple threads cannot access it simultaneously.
StringBuilder is identical to StringBuffer except for one important difference it is not synchronized, which means it is not thread safe.java training center bangalore Its because StringBuilder methods are not synchronised.
In other words, if multiple threads are accessing a StringBuilder instance at the same time, its integrity cannot be guaranteed. However, for a single thread program (most commonly), doing away with the overhead of synchronization makes the StringBuilder faster.
Difference between string , string buffer and string builder:
- String is immutable whereas StringBuffer and StringBuider are mutable classes.
- StringBuffer is thread safe and synchronized whereas StringBuilder is not, thats why StringBuilder is more faster than StringBuffer.
- String concat ,+ operator internally uses StringBuffer or StringBuilder class.
- For String manipulations in non-multi threaded environment, we should use Advance java training in bangalore StringBuilder else use StringBuffer class.
This is the short description about the String class.To get the more knowledge and to get the job as java developer easily join Infocampus Software Training Institute.
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