Consider the following example. String str = new String(); str = “Hello”; System.out.println(str); //Prints Hello str = “Help!”; System.out.println(str); //Prints Help! Now, in Java, String objects are immutable. Then how come the object str can be assigned value “Help!”. Isn’t this contradicting the immutability of strings in Java? Can anybody please explain me the exact … Read more
Closed. This question is opinion-based. It is not currently accepting answers. Closed last month. Locked. This question and its answers are locked because the question is off-topic but has historical significance. It is not currently accepting new answers or interactions. Sorry for the waffly title – if I could come up with a concise title, … Read more
I am currently working on React JS and React Native frameworks. On the half way road I came across Immutability or the Immutable-JS library, when I was reading about Facebook’s Flux and Redux implementation. The question is, why is immutability so important? What is wrong in mutating objects? Doesn’t it make things simple? Giving an … Read more
import copy a = “deepak” b = 1, 2, 3, 4 c = [1, 2, 3, 4] d = {1: 10, 2: 20, 3: 30} a1 = copy.copy(a) b1 = copy.copy(b) c1 = copy.copy(c) d1 = copy.copy(d) print(“immutable – id(a)==id(a1)”, id(a) == id(a1)) print(“immutable – id(b)==id(b1)”, id(b) == id(b1)) print(“mutable – id(c)==id(c1)”, id(c) == id(c1)) … Read more
I’ve recently come across the const keyword in JavaScript. From what I can tell, it is used to create immutable variables, and I’ve tested to ensure that it cannot be redefined (in Node.js): const x = ‘const’; const x = ‘not-const’; // Will give an error: ‘constant ‘x’ has already been defined’ I realise that … Read more
We all know that String is immutable in Java, but check the following code: String s1 = “Hello World”; String s2 = “Hello World”; String s3 = s1.substring(6); System.out.println(s1); // Hello World System.out.println(s2); // Hello World System.out.println(s3); // World Field field = String.class.getDeclaredField(“value”); field.setAccessible(true); char[] value = (char[])field.get(s1); value[6] = ‘J’; value[7] = ‘a’; value[8] … Read more
This could be the dumbest question ever asked but I think it is quite confusing for a Java newbie. Can somebody clarify what is meant by immutable? Why is a String immutable? What are the advantages/disadvantages of the immutable objects? Why should a mutable object such as StringBuilder be preferred over String and vice-verse? A … Read more
Following the discussions here on SO I already read several times the remark that mutable structs are “evil” (like in the answer to this question). What’s the actual problem with mutability and structs in C#? 16 s 16 Structs are value types which means they are copied when they are passed around. So if you … Read more
In Ruby some methods have a question mark (?) that ask a question like include? that ask if the object in question is included, this then returns a true/false. But why do some methods have exclamation marks (!) where others don’t? What does it mean? 10 s 10 In general, methods that end in ! … Read more
I’m trying to remove specific characters from a string using Python. This is the code I’m using right now. Unfortunately it appears to do nothing to the string. for char in line: if char in ” ?.!/;:”: line.replace(char,”) How do I do this properly? 26 s 26 Strings in Python are immutable (can’t be changed). … Read more
