在 Java 中实例化参数化类型(泛型)时传递原始值?
java 8object oriented programmingprogramming
泛型是 Java 中的一个概念，它允许类、接口和方法接受所有(引用)类型作为参数。换句话说，它允许用户动态选择方法(类的构造函数)接受的引用类型。通过将类定义为泛型，您可以使其具有类型安全，即它可以作用于任何数据类型。
示例
class Student<T>{
T age;
Student(T age){
this.age = age;
}
public void display() {
System.out.println("Value of age: "+this.age);
}
}
public class GenericsExample {
public static void main(String args[]) {
Student<Float> std1 = new Student<Float>(25.5f);
std1.display();
Student<String> std2 = new Student<String>("25");
std2.display();
Student<Integer> std3 = new Student<Integer>(25);
std3.display();
}
}
输出
Value of age: 25.5 Value of age: 25 Value of age: 25
传递原始值
泛型类型适用于引用类型，您不能将原始数据类型传递给它们，否则将生成编译时错误。
示例
class Student<T>{
T age;
Student(T age){
this.age = age;
}
}
public class GenericsExample {
public static void main(String args[]) {
Student<Float> std1 = new Student<Float>(25.5f);
Student<String> std2 = new Student<String>("25");
Student<int> std3 = new Student<int>(25);
}
}
编译时错误
GenericsExample.java:11: error: unexpected type Student<int> std3 = new Student<int>(25); ^ required: reference found: int GenericsExample.java:11: error: unexpected type Student<int> std3 = new Student<int>(25); ^ required: reference found: int 2 errors
示例
public class GenericMethod {
<T>void sampleMethod(T[] array) {
for(int i=0; i<array.length; i++) {
System.out.println(array[i]);
}
}
public static void main(String args[]) {
GenericMethod obj = new GenericMethod();
Integer intArray[] = {45, 26, 89, 96};
obj.sampleMethod(intArray);
String stringArray[] = {"Krishna", "Raju", "Seema", "Geeta"};
obj.sampleMethod(stringArray);
char charArray[] = {'a', 's', 'w', 't'};
obj.sampleMethod(charArray);
}
}
输出
GenericMethod.java:16: error: method sampleMethod in class GenericMethod cannot be applied to given types; obj.sampleMethod(charArray); ^ required: T[] found: char[] reason: inference variable T has incompatible bounds equality constraints: char upper bounds: Object where T is a type-variable: T extends Object declared in method <T>sampleMethod(T[]) 1 error
