英文:
Java overload: how to call more specific one
问题
以下是翻译好的内容：
我的程序解析 `WebAssembly` 指令，并根据当前指令的上下文进行决策。因此，我的算法的最小可行示例（MWE）如下所示：
public class Main {
public interface Context {
String name();
}
static class M implements Context {
public String name() {
return "Context M: ";
}
}
static class N implements Context {
public String name() {
return "Context N: ";
}
}
public interface Instruction {
int getId();
String run();
}
static class A implements Instruction {
public int getId() {
return 0;
}
public String run() {
return "A的工作";
}
}
static class B implements Instruction {
public int getId() {
return 1;
}
public String run() {
return "B的工作";
}
}
static void work(Context context, Instruction instruction) {
switch (instruction.getId()) {
case 0:
workOnId0(context, (A) instruction);
break;
case 1:
workOnId1(context, (B) instruction);
break;
default:
throw new RuntimeException("无法识别的指令");
}
}
static void workOnId0(Context context, A instruction) {
System.out.println(context.name() + instruction.run());
}
static void workOnId1(Context context, B instruction) {
System.out.println(context.name() + instruction.run());
}
static void workOnId1(N context, B instruction) {
System.out.println("这是针对该上下文的特殊逻辑！");
}
public static void main(String[] args) {
N context = new N();
B instruction = new B();
work(context, instruction);
}
}
正如你从上面所看到的，当我的指令是 B 时，普通的工作应该在 workOnId1 中发生，但是在上下文特定为 N 的情况下，我希望进行一些特殊的工作，这由 workOnId1 的不同重载表示。
不幸的是，特殊的重载从未被调用。我该如何使重载的解析工作？
英文:
My program parses WebAssembly instructions and makes decisions based on the context of the current instruction. So, the MWE for my algorithm looks like this:
public class Main {
public interface Context {
String name();
}
static class M implements Context {
public String name() {
return "Context M: ";
}
}
static class N implements Context {
public String name() {
return "Context N: ";
}
}
public interface Instruction {
int getId();
String run();
}
static class A implements Instruction {
public int getId() {
return 0;
}
public String run() {
return "The work of A";
}
}
static class B implements Instruction {
public int getId() {
return 1;
}
public String run() {
return "The work of B";
}
}
static void work(Context context, Instruction instruction) {
switch (instruction.getId()) {
case 0:
workOnId0(context, (A) instruction);
break;
case 1:
workOnId1(context, (B) instruction);
break;
default:
throw new RuntimeException("Failed to recognize instruction");
}
}
static void workOnId0(Context context, A instruction) {
System.out.println(context.name() + instruction.run());
}
static void workOnId1(Context context, B instruction) {
System.out.println(context.name() + instruction.run());
}
static void workOnId1(N context, B instruction) {
System.out.println("This is corner case logic for this context!");
}
public static void main(String[] args) {
N context = new N();
B instruction = new B();
work(context, instruction);
}
}
As you can see from above, when my instruction is B, then the ordinary work should happen in workOnId1, but in case my context is specifically N, I would like some special work done, which is represented by a different overload of workOnId1.
Unfortunately, the special overload never gets called. How can I make the overload resolution work?
答案1
得分: 0
workOnId1(Context context, B instruction) 将会始终被调用，因为您有一个 Context 对象。
您需要通过将调用方法转换为 N 来进行区分。如果这在您的模型内效果不佳，因为我猜这只是一个小例子，您可能需要重新思考整体设计。一个简单的解决方案是：
if (context instanceof N) {
workOnId1((N) context, (B) instruction);
} else {
workOnId1(context, (B) instruction);
}
英文:
workOnId1(Context context, B instruction) will always be called, because you have a Context object.
You are going to need to differentiate method calls by casting to N. If this doesn't work well within your model, since I'm guessing this is only a small example, you may need to rethink your overall design. A simple solution would be:
if(context instanceof N) {
workOnId1((N)context, (B)instruction);
} else {
workOnId1(context, (B) instruction);
}
答案2
得分: 0
你可以将 case:1 下的一行代码更改为以下内容，以实现你的目标：
switch (instruction.getId()) {
case 0:
workOnId0(context, (A) instruction);
break;
case 1:
workOnId1((context instanceof N) ? (N)context : context, (B) instruction);
break;
default:
throw new RuntimeException("无法识别的指令");
}
英文:
you can change one line under case:1 as below to achieve your target
switch (instruction.getId()) {
case 0:
workOnId0(context, (A) instruction);
break;
case 1:
workOnId1((context instanceof N)? (N)context :context, (B) instruction); break;
default:
throw new RuntimeException("Failed to recognize instruction");
}
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