class Foo {
private String id;
public Foo(String id) { this.id = id; }
public String getId() { return id; }
@Override
public String toString() { return id; }
}
List<Foo> list = Arrays.asList(new Foo("1"), new Foo("2"), new Foo("3"), new Foo("4"));
List<String> keys = Arrays.asList("2","1","3","4");
// before Java 8
List<Foo> result1 = new ArrayList<>(list);
Collections.sort(result1, new Comparator() {
@Override
public int compare(Foo o1, Foo o2) {
return keys.indexOf(o1.getId()) < keys.indexOf(o2.getId()) ? -1 : 1;
}
});
// after Java 8
List<Foo> result2 = list.stream()
.sorted(Comparator.comparing(e -> keys.indexOf(e.getId())))
.collect(Collectors.toList());
System.out.println(result1); // [2, 1, 3, 4]
System.out.println(result2); // [2, 1, 3, 4]
2018年5月31日 星期四
[Java] 使用另一個列表進行排序
2018年5月28日 星期一
[PHP] unique values & resort keys
function calc($t0, $t1)
{
$v0 = array_sum(explode(' ', $t0));
$v1 = array_sum(explode(' ', $t1));
$sub = $v1 - $v0;
echo "$v1 - $v0 = $sub\n";
return $sub;
}
$a = [116,116,116,116,116,116,116,116,116,116,116,116,116,116,116,116,117,116,117,116,116,116,116,116,119];
$t0 = microtime();
for ($i = 0; $i < 1E6; $i++) {
array_values(array_unique($a));
}
$t1 = microtime();
$method1 = calc($t0, $t1); // output: 1527477436.7125 - 1527477409.434 = 27.278562068939
$t0 = microtime();
for ($i = 0; $i < 1E6; $i++) {
array_keys(array_flip($a));
}
$t1 = microtime();
$method2 = calc($t0, $t1); // output: 1527477439.6214 - 1527477436.7126 = 2.908814907074
$t0 = microtime();
for ($i = 0; $i < 1E6; $i++) {
array_merge(array_flip(array_flip($a)));
}
$t1 = microtime();
$method3 = calc($t0, $t1); // output: 1527477443.3256 - 1527477439.6215 = 3.7041912078857
有時候直覺的方式會比較慢。
參考資料：http://php.net/manual/en/function.array-unique.php#70786
PHP 5.6.36 (cli) (built: May 9 2018 20:31:47)
Copyright (c) 1997-2016 The PHP Group
Zend Engine v2.6.0, Copyright (c) 1998-2016 Zend Technologies
with Xdebug v2.3.3, Copyright (c) 2002-2015, by Derick Rethans
2018年5月8日 星期二
[Java] find enum with Java 8 streams
import java.util.EnumSet;
public enum Status {
PENDING("pending"),
ACTIVE("active");
public static final Status fromString(String status) {
return Stream.of(Status.values)
.filter(e -> e.status.equals(status))
.findAny();
.orElseThrow(() -> new IllegalArgumentException("No enum constant " + status));
}
private final String status;
private Status(String status) {
this.status = status;
}
@Override
public String toString() {
return status;
}
}
參考資料：
[Java] running JAX-RS with gretty
開一個專案叫 jersey，然後按下面加入代碼：
// build.gradle
plugins {
id 'war'
//id 'org.gretty' version '2.1.0'
id 'org.akhikhl.gretty' version '2.0.0'
}
// 'jetty7', 'jetty8', 'jetty9', 'jetty9.3', 'jetty9.4', 'tomcat7', 'tomcat8'
//gretty.servletContainer='jetty9'
repositories {
jcenter()
}
dependencies {
compile 'org.glassfish.jersey.containers:jersey-container-servlet:2.26'
compile 'org.glassfish.jersey.inject:jersey-hk2:2.27'
}
// src/main/webapp/WEB-INF/web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
id="WebApp_ID"
version="3.0">
<display-name>My JAX-RS</display-name>
<servlet>
<servlet-name>jersey-servlet</servlet-name>
<servlet-class>org.glassfish.jersey.servlet.ServletContainer</servlet-class>
<init-param>
<param-name>jersey.config.server.provider.packages</param-name>
<param-value>demo</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>jersey-servlet</servlet-name>
<url-pattern>/*</url-pattern>
</servlet-mapping>
</web-app>
// src/main/java/demo/Hello.java
package demo;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.core.Response;
@Path("/hello")
public class Hello {
@GET()
public String hello() {
return "hello";
}
@GET
@Path("/{name}")
public Response getMessage(@PathParam("name") String name) {
String outMsg = "Hello " + name + "!";
return Response.status(200).entity(outMsg).build();
}
}
接下來執行 gradle appRun
$ gradle appRun :prepareInplaceWebAppFolder UP-TO-DATE :createInplaceWebAppFolder UP-TO-DATE :compileJava :processResources NO-SOURCE :classes :prepareInplaceWebAppClasses :prepareInplaceWebApp :appRun 19:46:58 INFO Jetty 9.2.24.v20180105 started and listening on port 8080 19:46:58 INFO JAX-RS Application Demo runs at: 19:46:58 INFO http://localhost:8080/jersey > Task :appRun Press any key to stop the server. <===========--> 87% EXECUTING [17s] > :appRun
然後就可以測試了：
- http://localhost:8080/jersey/hello
- http://localhost:8080/jersey/hello/John
備註：
- web.xml 的 "param-value" 必須跟套件名一樣，jersey 才會作用。
- 用 gretty 試跑的時候，URL 是帶上專案名稱，像這裡是 "/jersey"。放在 Servlet 上面跑的時候則是看檔案名稱，例如 "jersey.war"；如果不想要這個路徑，可以改成 "ROOT.war"。
- web.xml 預設路徑是
src/main/webapp/WEB-INF，但是可以在 Gradle 的 war plugin 設定。
備註２：Servlet 3 之後可以不寫 web.xml，改成繼承 ResourceConfig。
// src/main/java/demo/MyApplication.java
package demo;
import javax.ws.rs.ApplicationPath;
import org.glassfish.jersey.server.ResourceConfig;
@ApplicationPath("/")
public class MyApplication extends ResourceConfig {
public MyApplication() {
packages("demo");
}
}
備註３：如果 gretty 發生 Java9 相容問題，
Caused by: java.lang.RuntimeException: Error scanning entry META-INF/versions/9/module-info.class from jar file: .gradle/caches/modules-2/files-2.1/... Caused by: java.lang.RuntimeException: Error scanning entry module-info.class from jar file: .gradle/caches/modules-2/files-2.1/...可以設定參數
gretty.servletContainer 為 "jetty9.4" 或是 "tomcat8" 測試。
參考資料：
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