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What is constant pool?
Simply put, a constant pool contains the constants that are needed to run the code of a specific class. It is a per-class or per-interface runtime representation in a Java class file. The content of the constant pool consists of symbolic references generated by the compiler.
What is the use of string constant pool in Java?
The String constant pool is a special memory area. When we declare a String literal, the JVM creates the object in the pool and stores its reference on the stack. Before creating each String object in memory, the JVM performs some steps to decrease the memory overhead.
How is string constant pool maintained?
JVM checks the String constant pool first and if the string does not exist, it creates a new String object “iByteCode” and a reference is maintained in the pool. String s2 = “iByteCode” ; JVM checks the String constant pool first and since the string already exists, a reference to the pooled instance is returned to s2.
What is static constant pool?
A constant pool is an ordered set of constants used by the type, including literals (string, integer, and floating point constants) and symbolic references to types, fields, and methods. Entries in the constant pool are referenced by index, much like the elements of an array.
What will s2 contain After following lines of code?
What will s2 contain after following lines of Java code? Explanation: Two strings can be concatenated by using concat() method. 3.
Is string pool garbage collected in Java?
The risk of interning Strings in the PermGen (instead of the Heap) is that we can get an OutOfMemory error from the JVM if we intern too many Strings. From Java 7 onwards, the Java String Pool is stored in the Heap space, which is garbage collected by the JVM.
Can we make constructor static?
No, we cannot define a static constructor in Java, If we are trying to define a constructor with the static keyword a compile-time error will occur. A constructor will be used to assign initial values for the instance variables. Both static and constructor are different and opposite to each other.
Why do we have a constant pool in Java?
In other words, the string constant pool exists mainly to reduce memory usage and improve the re-use of existing instances in memory. When a string object is assigned a different value, the new value will be registered in the string constant pool as a separate instance. Lets understand this with the following example:
What’s the difference between a string pool and a constant pool?
Both variables refer to the same object due to interning. Since strings are immutable, only one object is created and both refer to the same object. A constant pool is also something, which holds all the constants (integer, string, etc.) that are declared in a class. It is specific to each class.
Where does the new instance go in the string constant pool?
Using ‘new’ forces the instance to be created in the heap outside the string constant pool which is clear, since caching and re-using of instances isn’t allowed here. Let’s understand this with an example: The following illustration explains the memory allocation for the above declaration:
What do you call a constant in Java?
Java has a different naming convention for constants. It isn’t the usual camelCase notation. If it had been an ordinary variable, we would have called it constantExample. But, the names of constants are written in all caps, with underscores between words (if there is more than one word), e.g. “CONSTANT_EXAMPLE”.