Java By Source

While coding in any programming language we always require some predefined types which we can use to write the code and every programming language provides these types in its way e.g. Java provides primitive types ( int, long, char float etc) and reference types (custom types like Object, String, Thread ). For string manipulation, Java provides a class java.lang.String which gives us a way to create string objects and provides different behaviors to operate on those objects e.g. replace(), length() String name = "Naresh"; System.out.print(name.length()); System.out.print(name.isEmpty()); Whenever we talk about String class in Java we say it is i mmutable in nature and all string literals are stored in String Constant Pool (SCP) . Prior to Java 7 String Constant Pool belongs to Permanent Generation area of heap which means Garbage Collector will not touch it in normal scenarios. But from Java 7 onwards string constant pool is not part of Perm Gen but live with o

In a previous article Why String is Immutable and Final in Java , I have discussed why String is immutable in nature and advantages and disadvantages String's immutability gives us. I have also discussed that, all String literals are cached into a special memory area called String Constant Pool and how String's immutability made String constant pool possible. But the question arises why do Java required a separate constant pool to store Strings, What's the reason, Why strings are not stored in the normal heap memory like other objects do and in this article, I will try to answer these questions. String Interning Well, we know String is the most popular type present in Java and almost all Java programs use it. In fact, I have not seen a single Java program which is written without using String. In general, a normal Java business application deals with thousands of string objects, lots of them have same value associated and lots of them are mid operations string means they a

Java allows us to declare a variable whenever we need it, We can categorize all our variables into 3 categories which have different-different scopes Instance Variables - Defined inside a class and have object level scope. Class Variables - Defined inside a class with static keyword, have class level scope common to all objects of the same class Local Variables - Defined inside a method or in any conditional block, have the block-level scope and only accessible in the block where it defined. What is Variable Shadowing Variable shadowing happens when we define a variable in a closure scope with a variable name and we have already defined a variable in outer scope with the same name. In other words, when a local variable has the same name as one of the instance variable, the local variable shadows the instance variable inside the method block. In the following example, there is an instance variable named x and inside method printLocalVariable(), we are shadowing it by the local vari