java泛型

泛型只在编译期有效，运行期无效

@org.junit.Test
public void demo01() {
    ArrayList<String> list = new ArrayList<>();
    ArrayList<Integer> list2 = new ArrayList<>();
    System.out.println(list.equals(list2)); // 输出：true
}

泛型类

public class Generic<T> {
    private T type;

    public Generic(T type) {
        this.type = type;
    }

    public T getType() {
        return type;
    }

    public void setType(T type) {
        this.type = type;
    }
}

泛型方法

public <V> V getGeneric(V v) {
    System.out.println(v);
    return v;
}

泛型通配符

public class Generic<T> {
    // 参数list的类型必须与Generic的实例类型一致
    public void a(List<T> list) {
        System.out.println(list);
    }

    // 参数list的类型无限制
    public void b(List<?> list) {
        System.out.println(list);
    }

    public static void main(String[] args) {
        Generic<String> generic = new Generic<>();
        generic.a(new ArrayList<>());
        generic.b(new ArrayList<Integer>());
    }
}