immutability

This question already has answers here : Why are python strings and tuples are made immutable? (6 answers) Possible Duplicate: Why are python strings and tuples are made immutable? What lower-level design makes tuple not mutable in Python? Why this feature is useful? A few reasons: Mutable objects like lists cannot be used as dictionary keys or set members in Python, since they are not hashable . If lists were given __hash__ methods based on their contents, the values returned could change as the contents change, which violates the contract for hash values. If Python only had mutable sequences

This question already has answers here : Why is the String class declared final in Java? (16 answers) As i was told this is important String Interview question in Java, which starts with discussion of " What is String ", how String is different in java than in C or C++ and then you are asked about immutable objects and you're asked the main question: " Why String is immutable or final in Java ". Can you share your Ideas ? Thanks in advance. It is mainly for security reasons . String is used as parameter in network connection, database url etc. It can be easily attacked if it is mutable

Can we create an immutable object without having all fields final? If possible a couple of examples would be helpful. Declare all fields private and only define getters: public final class Private{ private int a; private int b; public int getA(){return this.a;} public int getB(){return this.b;} } citing @Jon Skeet's comment, final class modifier is useful for: While an instance of just Private is immutable, an instance of a subclass may well be mutable. So code receiving a reference of type Private can't rely on it being immutable without checking that it's an instance of just Private. So if

We know the concept of immutability but need to know few immutable types other than String DateTime Are there more? stakx A list of immutable types in the framework class library follows below. (Feel free to expand it!) System.… All primitive value types: (Note: not all value types are immutable !) Byte and SByte Int16 and UInt16 Int32 and UInt32 Int64 and UInt64 IntPtr Single Double Decimal All anonymous types created by the compiler ( new { ... } in C#, New With { ... } in VB.NET) (Wrong for two reasons: These types are not in the FCL, and apparently VB.NET types are mutable.) All

I have a question regarding the Java Memory Model. Here is a simple class presenting the problem: public class ImmutableIntArray { private final int[] array; public ImmutableIntArray() { array = new int[10]; for (int i = 0; i < 10; i++) { array[i] = i; } } // Will always return the correct value? public int get(int index) { return array[index]; } } As far as I know the JMM guarantees that the value of final fields will be visible to other threads after construction. But I want to ensure that other threads will see the most recent version of data stored in the array after construction. Of

Why won't declaring an array final make it immutable in Java? Doesn't declaring something final mean it can't be changed? From question related to immutable array it's clear that declaring an array final doesn't make it unchangeable. The following is possible. final int[] array = new int[] {0, 1, 2, 3}; array[0] = 42; My question is: What is the function of declaring final here then? final is only about the reference that is marked by it; there is no such thing as an immutable array in Java. When you say private final int[] xs = new int[20]; you won't be allowed to say xs = new int[10]; later