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[英]How to call a method whose name is the value of a string variable in java?
[英]How to call a method by name (String) in Java?
類A<\/code>每個實例都有一個類
B<\/code>的實例。
A<\/code>應該根據其成員變量
method_num<\/code>在
B<\/code>調用不同的方法。這是一個實現我想要的實現:
public class A {
private B myB = new B();
public int method_num = 1;
public callBMethod() {
if ( method_num == 1 )
myB.method1();
else
myB.method2();
}
}
public class B {
public method1() { }
public method2() { }
}
如果您不想使用反射(這是一個很好的目標),那么enum
有一些簡潔的功能可以讓您將enum
設置為代理。
public class A {
private B myB = new B();
public int method_num = 1;
public void callBMethod() {
// Could do it by name.
BMethods.valueOf("method1").call(myB);
// Or by number.
BMethods.values()[method_num].call(myB);
}
}
enum BMethods{
method1 {
@Override
public void call(B b) {
b.method1();
}
},
method2 {
@Override
public void call(B b) {
b.method2();
}
};
public abstract void call (B b);
}
public class B {
public void method1() {
}
public void method2() {
}
}
你不能。 Java 不將函數視為第一類對象,因為它沒有 Python 或 C# 之類的函數特性。
您可以創建一個 Command 接口並傳遞該對象引用:
public interface Command {
void execute(Object [] args);
}
我認為您可以像這樣使用反射:
java.lang.reflect.Method method;
try {
method = obj.getClass().getMethod(methodName, param1.class, param2.class, ..);
} catch (SecurityException e) {
// ...
} catch (NoSuchMethodException e) {
// ...
}
try {
method.invoke(obj, arg1, arg2,...);
} catch (IllegalArgumentException e) { //do proper handling
} catch (IllegalAccessException e) {//do proper handling
} catch (InvocationTargetException e) {//do proper handling
也許與Runnable
對象? 您可以從 B 傳遞一個可運行文件,並直接從 A 調用.run()
Java 反射 API 為您提供了一種方法,可以將 Method 類型的對象與目標對象一起傳遞,然后可以在目標對象上調用該方法。
示例如下:
Method m; // The method to be invoked
Object target; // The object to invoke it on
Object[] args; // The arguments to pass to the method
// An empty array; used for methods with no arguments at all.
static final Object[] nullargs = new Object[] {};
/** This constructor creates a Command object for a no-arg method */
public Command(Object target, Method m) {
this(target, m, nullargs);
}
/**
* This constructor creates a Command object for a method that takes the
* specified array of arguments. Note that the parse() method provides
* another way to create a Command object
*/
public Command(Object target, Method m, Object[] args) {
this.target = target;
this.m = m;
this.args = args;
}
/**
* Invoke the Command by calling the method on its target, and passing the
* arguments. See also actionPerformed() which does not throw the checked
* exceptions that this method does.
*/
public void invoke() throws IllegalAccessException,
InvocationTargetException {
m.invoke(target, args); // Use reflection to invoke the method
}
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