The constructor is an unusual type of method because it has no return value. This is distinctly different from a void return value, in which the method returns nothing but you still have the option to make it return something else. Constructors return nothing and you don’t have an option ...
PARAMETER,/** Formal parameter declaration 该注解可以用在参数上*/ CONSTRUCTOR,/** Constructor declaration 该注解可以用在构造器上*/ LOCAL_VARIABLE,/** Local variable declaration 该注解可以用在局部变量上*/ ANNOTATION_TYPE,/** Annotation type declaration 该注解可以用在注解类型上 */ PACKAGE,/** Pack...
The No-arg constructor is a constructor that accepts no arguments. If we don’t define a constructor in a class, the compiler automatically builds one for the class (with no arguments). Additionally, the compiler does not produce a default constructor if we write a constructor with arguments ...
public @interface TestAnnotation { int value() default 0; String desc() default "no desc"; } 1. 2. 3. 4. 5. 上例中我们定义了一个名为TestAnnotation的注解,注解是用关键字@interface来定义的,大括号内的方法称为注解的元素,注解和接口很相似,区别是注解元素可以为其指定初始值,default关键字用来指...
反射可以获取到Class对象，进而获取到Constructor、Field、Method等实例，点开源码结构发现Class、Constructor、Field、Method等均实现了AnnotatedElement接口，AnnotatedElement接口的方法如下 // 判断该元素是否包含指定注解，包含则返回trueboolean isAnnotationPresent(Class<? extends Annotation> annotationClass)// 返回该元素...
//default constructor publicExample2() { this.var =10; } //parameterized constructor publicExample2(intnum) { this.var = num; } publicintgetValue() { returnvar; } publicstaticvoidmain(String args[]) { Example2 obj =newExample2(); ...
lang.annotation.Retention;import java.lang.annotation.RetentionPolicy;import java.lang.annotation.Target;@Target(ElementType.CONSTRUCTOR) // 用于构造方法@Retention(RetentionPolicy.RUNTIME) // 在运行时加载Annotation到JVM中public @interface Constructor_Annotation{ String value() default "默认构造方法...
Returns a hashcode for this Constructor. The hashcode is the same as the hashcode for the underlying constructor's declaring class name. Overrides: hashCode in class Object Returns: a hash code value for this object. See Also: Object.equals(java.lang.Object), System.identityHashCode(java.lang....
variable没有default value,必须在constructor (构造器)结束之前被赋予一个明确的值。可以修改为"final int i = 0;"。 (8) 下面这段代码看上去很完美,错在哪里呢? public class Something { public static void main(String[] args) { Something s = new Something(); System.out.println("s.doSomething()...
constructor. Only the Java Virtual Machine creates Class objects. //私有构造器,只有JVM才能调用创建Class对象* This constructor is not used and prevents the default constructor being* generated.*/private Class(ClassLoader loader) {// Initialize final field for classLoader. The initialization value of ...