我如何使用java模板实现这个方法? [英] how can I implement this method using java template?
问题描述
创建一个接口(使用模板):
package util.filter;
public interface Filter< INPUT,OUTPUT> {
public OUTPUT filter(INPUT mes);
$ / code>
和一个实现的类(仅用于测试):
package util.filter;
public static class TestImplFilter implements Filter< Integer,String> {
public String filter(Integer i){
returnHello World!;
}
}
我可以使用这段代码来测试:
过滤<整数,字符串> f = new TestImplFilter();
System.out.println(f.filter(123));
//输出:Hello World!
现在,我要创建一个静态方法,
使用impl类路径( util.filter.TestImplFilter
)作为参数,
和 INPUT 作为第二个参数,并返回一个 OUTPUT 。
所以,我写了下面的代码:
private static Object createInstance(String classPath){
try {
Class<?> tClass = Class.forName(classPath);
if(tClass!= null){
return tClass.newInstance();
}
} catch(Exception e){
e.printStackTrace();
}
返回null;
}
public final static Filter<?,?> getFilter(String path){
return(Filter<?,?>)createInstance(path);
}
//我在这里的问题:
public final static OUTPUT filter(String path,INPUT mes){
Filter< ?,?> filter =(Filter <?,?>)createInstance(path);
return filter.filter(mes);
我的问题在静态方法 filter(String path, INPUT mes)
,这段代码是错误的。
我该如何解决它并实现这个方法?
感谢您的帮助:)
我的错误,我捣乱了命令,现在是正确
您也可以为静态方法指定泛型。为此,请在返回参数之前添加gereric模板信息:
public final static< INPUT,OUTPUT> OUTPUT filter(String path,INPUT mes){
然后编译。
public class Test {
private static Object createInstance(String classPath){
try {
Class<?> tClass = Class.forName(classPath);
if(tClass!= null){
return tClass.newInstance();
}
} catch(Exception e){
e.printStackTrace();
}
返回null;
}
@SuppressWarnings(unchecked)
public final static< INPUT,OUTPUT>过滤< INPUT,OUTPUT> getFilter(String path){
return(Filter< INPUT,OUTPUT>)createInstance(path);
}
public final static< INPUT,OUTPUT> OUTPUT过滤器(字符串路径,INPUT消息){
过滤< INPUT,OUTPUT> filter = getFilter(path);
return filter.filter(mes);
}
}
create a interface(using template):
package util.filter;
public interface Filter<INPUT,OUTPUT> {
public OUTPUT filter(INPUT mes);
}
and an implemented class (only for test):
package util.filter;
public static class TestImplFilter implements Filter<Integer,String>{
public String filter(Integer i){
return "Hello World!";
}
}
I can using this code to test:
Filter<Integer,String> f=new TestImplFilter();
System.out.println(f.filter(123));
//output: Hello World!
now,I want create a static method,
using impl class path (util.filter.TestImplFilter
) as an argument,
and INPUT as second argument, and return a OUTPUT.
so, I writed follow code:
private static Object createInstance(String classPath) {
try {
Class<?> tClass = Class.forName(classPath);
if (tClass != null) {
return tClass.newInstance();
}
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
public final static Filter<?,?> getFilter(String path){
return (Filter<?,?>)createInstance(path);
}
//my problem in here:
public final static OUTPUT filter(String path,INPUT mes){
Filter<?,?> filter = (Filter<?, ?>) createInstance(path);
return filter.filter(mes);
}
my problem in static method filter(String path,INPUT mes)
, this code is error.
how can I fix it and implement this method?
thanks for help :)
my mistake, I mashed the order, now it is correct
You can specifiy generics for static methods too. To do that, add the gereric template information ahead of the return parameter:
public final static<INPUT,OUTPUT> OUTPUT filter(String path,INPUT mes){
then it will compile.
public class Test {
private static Object createInstance(String classPath) {
try {
Class<?> tClass = Class.forName(classPath);
if (tClass != null) {
return tClass.newInstance();
}
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
@SuppressWarnings("unchecked")
public final static <INPUT, OUTPUT> Filter<INPUT, OUTPUT> getFilter(String path) {
return (Filter<INPUT, OUTPUT>) createInstance(path);
}
public final static <INPUT, OUTPUT> OUTPUT filter(String path, INPUT mes) {
Filter<INPUT, OUTPUT> filter = getFilter(path);
return filter.filter(mes);
}
}
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