constants

问题 Please help me understand the difference between constant variables and final variables in Java. I am a bit confused with it. 回答1: Constant is the concept, the property of the variable. final is the java keyword to declare a constant variable. As other people pointed out, from a semantic/linguistic point of view the expression constant variable is an oxymoron and, as such, we could argue about its correctness. Quoting the specification, anyway, we can read A variable of primitive type [...],

问题 Please help me understand the difference between constant variables and final variables in Java. I am a bit confused with it. 回答1: Constant is the concept, the property of the variable. final is the java keyword to declare a constant variable. As other people pointed out, from a semantic/linguistic point of view the expression constant variable is an oxymoron and, as such, we could argue about its correctness. Quoting the specification, anyway, we can read A variable of primitive type [...],

问题 This question already has answers here : Java switch statement: Constant expression required, but it IS constant (13 answers) Closed 4 years ago . I was working on switch case. If we use class.getName(), then, I am getting error that "case expressions must be constant expressions" as follows: switch(param.getClass().getName()) { case String.class.getName(): // to do break; } Even if we do following, take string class name in a constant, then also, getting same error: public static final

问题 This question already has answers here : Java switch statement: Constant expression required, but it IS constant (13 answers) Closed 4 years ago . I was working on switch case. If we use class.getName(), then, I am getting error that "case expressions must be constant expressions" as follows: switch(param.getClass().getName()) { case String.class.getName(): // to do break; } Even if we do following, take string class name in a constant, then also, getting same error: public static final

问题 This question already has answers here : Java switch statement: Constant expression required, but it IS constant (13 answers) Closed 4 years ago . I was working on switch case. If we use class.getName(), then, I am getting error that "case expressions must be constant expressions" as follows: switch(param.getClass().getName()) { case String.class.getName(): // to do break; } Even if we do following, take string class name in a constant, then also, getting same error: public static final

问题 I know Swift does encourage us programmers to use constants ( let ) instead of variables ( var ) everytime it makes sense. This is a good thing because we are providing more details to the compiler about what our code means and the compiler can better prevent us from making mistakes (e.g. changing some value that should not be changed). My question is, are there some performance optimizations the compiler does apply when we use constants instead of variables ? (e.g. faster executions times,

问题 What is the best way to accomplish the following in C? #include <stdio.h> struct A { int x; }; struct A createA(int x) { struct A a; a.x = x; return a; } struct A a = createA(42); int main(int argc, char** argv) { printf("%d\n", a.x); return 0; } When I try to compile the above code, the compiler reports the following error: "initializer element is not constant" The bad line is this one: struct A a = createA(42); Can someone explain what is wrong? I'm not very experienced in C. Thanks! 回答1:

问题 What is the best way to accomplish the following in C? #include <stdio.h> struct A { int x; }; struct A createA(int x) { struct A a; a.x = x; return a; } struct A a = createA(42); int main(int argc, char** argv) { printf("%d\n", a.x); return 0; } When I try to compile the above code, the compiler reports the following error: "initializer element is not constant" The bad line is this one: struct A a = createA(42); Can someone explain what is wrong? I'm not very experienced in C. Thanks! 回答1:

问题 This question already has answers here : How do I create a global, mutable singleton? (2 answers) How can you make a safe static singleton in Rust? (2 answers) Closed 4 days ago . I'm trying to port a Go language chess engine ( https://github.com/easychessanimations/gobbit ) to Rust ( https://github.com/easychessanimations/rustengine ). Problem with Go is that it produces a WASM executable which is bloated in size because it contains the whole Go runtime ( > 2 MB ). Also the native executable

问题 This question already has answers here : How do I create a global, mutable singleton? (2 answers) How can you make a safe static singleton in Rust? (2 answers) Closed 4 days ago . I'm trying to port a Go language chess engine ( https://github.com/easychessanimations/gobbit ) to Rust ( https://github.com/easychessanimations/rustengine ). Problem with Go is that it produces a WASM executable which is bloated in size because it contains the whole Go runtime ( > 2 MB ). Also the native executable