如何将Set直接转成数组
我家有只小熊二 人气:0Set直接转成数组
例子
public class Test{ public void test1(){ Set<String> set = new HashSet<>(); set.add("1"); set.add("2"); set.add("3"); set.add("4"); set.add("5"); set.add("6"); } }
错误方式:
String[] arr = (String[]) set.toArray(); for(String str: arr){ System.out.println(str) }
正确的方式:
String[] arr = set.toArray(new String[set.size()]); for(String str: arr){ System.out.println(str) }
Set,List转String数组
Set转String数组直接用其toArray()方法即可
注意事项如下
Object[] array = set.toArray();
// 错误!!!!!!!
String[] targetFail = (String[]) array;
错误信息如下:
ERROR 2019-06-04 17:43:13 [http-nio-9008-exec-7] com.wii.spring.framework.exception.GlobalExceptionResolver.exceptionHandler(GlobalExceptionResolver.java:106) - error:[Ljava.lang.Object; cannot be cast to [Ljava.lang.String;
java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to [Ljava.lang.String;
at com.zjht.controller.OrderController.export(OrderController.java:457) ~[classes!/:0.0.1-SNAPSHOT]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_201]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_201]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_201]
at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_201]
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:209) ~[spring-web-5.0.12.RELEASE.jar!/:5.0.12.RELEASE]
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:136) ~[spring-web-5.0.12.RELEASE.jar!/:5.0.12.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:102) ~[spring-webmvc-5.0.12.RELEASE.jar!/:5.0.12.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:891) ~[spring-webmvc-5.0.12.RELEASE.jar!/:5.0.12.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:797) ~[spring-webmvc-5.0.12.RELEASE.jar!/:5.0.12.RELEASE]
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.0.12.RELEASE.jar!/:5.0.12.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:991) [spring-webmvc-5.0.12.RELEASE.jar!/:5.0.12.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:925) [spring-webmvc-5.0.12.RELEASE.jar!/:5.0.12.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:981) [spring-webmvc-5.0.12.RELEASE.jar!/:5.0.12.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:873) [spring-webmvc-5.0.12.RELEASE.jar!/:5.0.12.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:635) [tomcat-embed-core-8.5.37.jar!/:8.5.37]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:858) [spring-webmvc-5.0.12.RELEASE.jar!/:5.0.12.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:742) [tomcat-embed-core-8.5.37.jar!/:8.5.37]
正确转换如下
private static void methodTwo(Set<String> set) { Object[] array = set.toArray(); // 错误!!!!!!! String[] targetFail = (String[]) array; for (String str : targetFail) { System.out.println("目标数组:" + str); } // 正确 String[] targetSuccess = set.toArray(new String[set.size()]); for (String str : targetSuccess) { System.out.println("目标数组:" + str); } }
以上为个人经验,希望能给大家一个参考,也希望大家多多支持。
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