英文:
Variable referencing from a lambda expression in Java
问题
以下是您提供的翻译内容：
为什么 Java 允许这样，
class Test {
boolean a;
public void test() {
...
object.method(e -> a = true);
}
}
但不允许这样，
class Test {
public void test() {
boolean a;
...
object.method(e -> a = true);
}
}
对于第二个示例，它会抛出：
local variables referenced from a lambda expression must be final or effectively final
第二个示例的唯一区别是变量是在方法内部声明的，而不是在类本身声明的。作为 Java 编程的初学者，我是否漏掉了一些明显的内容？
英文:
Why does Java allow this,
class Test {
boolean a;
public void test() {
...
object.method(e -> a = true);
}
}
But not this,
class Test {
public void test() {
boolean a;
...
object.method(e -> a = true);
}
}
For the second example, it throws:
local variables referenced from a lambda expression must be final or effectively final
The only difference in second example is that the variable is declared inside the method instead of the class itself. I am a beginner in Java programming, am I missing something obvious?
答案1
得分: 5
第一个示例有效，因为a = true实际上是this.a = true的速记，而且this始终是final（正如Java规范所述）。
英文:
The first example works, because a = true is actually shorthand for this.a = true, and this is always final (so says the Java Specification).
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