diamond-operator

Java 7 Diamond Operation in method call

由 与世无争的帅哥 提交于 2021-01-27 02:58:50
问题 This is kind of a follow up question on the discussion: Why doesn't the diamond operator work within a addAll() call in Java 7? From the Java Tutorial, http://docs.oracle.com/javase/tutorial/java/generics/gentypeinference.html Note that the diamond often works in method calls; however, for greater clarity, it is suggested that you use the diamond primarily to initialize a variable where it is declared So, I am a bit confused about the first line. When does diamond work in method calls? A bit

Java 7 Diamond Operation in method call

由 笑着哭i 提交于 2021-01-27 02:57:12
问题 This is kind of a follow up question on the discussion: Why doesn't the diamond operator work within a addAll() call in Java 7? From the Java Tutorial, http://docs.oracle.com/javase/tutorial/java/generics/gentypeinference.html Note that the diamond often works in method calls; however, for greater clarity, it is suggested that you use the diamond primarily to initialize a variable where it is declared So, I am a bit confused about the first line. When does diamond work in method calls? A bit

Why can't Java 7 diamond operator be used with anonymous classes?

由 只愿长相守 提交于 2019-12-28 12:16:08
问题 Consider this Java code which attempts to instantiate some List s: List<String> list1 = new ArrayList<String>(); List<String> list2 = new ArrayList<>(); List<String> list3 = new ArrayList<String>() { }; List<String> list4 = new ArrayList<>() { }; List<String> list5 = new ArrayList<Integer>() { }; list1 and list2 are straightforward; list2 uses the new diamond operator in Java 7 to reduce unnecessary repetition of the type parameters. list3 is a variation on list1 using an anonymous class,

How to fake input to perl's diamond operator?

由 雨燕双飞 提交于 2019-12-22 02:05:24
问题 The answers to this question describe how to fake input to <STDIN> . My goal is similar to that question: my unit test needs to fake input to <> . When I apply the same technique to fake input to <> , it doesn't work. The introductory-level explanations of <> led me to believe that it was reading from STDIN when no files are given on the command line, but this doesn't seem to be the case. The sample I'm trying to make work: #!/usr/bin/perl -w use strict; use warnings; use Carp; use English qw

How to fake input to perl's diamond operator?

由 笑着哭i 提交于 2019-12-22 02:05:22
问题 The answers to this question describe how to fake input to <STDIN> . My goal is similar to that question: my unit test needs to fake input to <> . When I apply the same technique to fake input to <> , it doesn't work. The introductory-level explanations of <> led me to believe that it was reading from STDIN when no files are given on the command line, but this doesn't seem to be the case. The sample I'm trying to make work: #!/usr/bin/perl -w use strict; use warnings; use Carp; use English qw

Why explicit type argument should be replaced by diamond? [duplicate]

由 喜欢而已 提交于 2019-12-18 11:08:22
问题 This question already has answers here : What is the point of the diamond operator (<>) in Java 7? (7 answers) Closed 4 years ago . I'm using Android Studio and I write this : List<Button> buttons = new ArrayList<Button>(); I have this message : Explicit type argument Button should be replaced by <> I'm curious, why would it be better to use diamond instead ? List<Button> buttons = new ArrayList<>(); EDIT : I don't agree with the duplicate at all ! I saw that answer before and it compares

Using Generics on right hand side in Java 6?

由 我与影子孤独终老i 提交于 2019-12-12 14:44:59
问题 I java 6 i can declare the arraylist as follows Way1: using generics i.e <Integer> on right hand side too List<Integer> p = new ArrayList<Integer>(); Way2: using the diamond operator List<Integer> p = new ArrayList<>(); Way3: using generic only at left side List<Integer> p = new ArrayList(); I prefer to use way 3 as its brief. Is there any difference between these ways? Which one we should prefer and why? Update:- I know in java 7 second way is recommended but my question is in context of

Diamond type are not supported at this language level

由 你离开我真会死。 提交于 2019-12-05 20:54:08
问题 After importing a project into Android studio, if I want to compile or run the project it throws an error: Error:(61, 65) java: diamond operator is not supported in -source 1.6 (use -source 7 or higher to enable diamond operator) Does anyone know what it is and how to solve it ? 回答1: In Android Studio (File -> Project Structure..., Properties tab), set the following values: Source Compatibility == 1.7 Target Compatibility == 1.7 After this your build.gradle will have these entries:

Why doesn't the diamond operator work within a addAll() call in Java 7?

由 淺唱寂寞╮ 提交于 2019-12-01 15:23:27
Given this example from the generics tutorial . List<String> list = new ArrayList<>(); list.add("A"); // The following statement should fail since addAll expects // Collection<? extends String> list.addAll(new ArrayList<>()); Why does the last line not compile, when it seems it should compile. The first line uses a very similar construct and compiles without a problem. Please explain elaborately. First of all: unless you're using Java 7 all of this will not work, because the diamond <> has only been introduced in that Java version. Also, this answer assumes that the reader understands the

Java 7 diamond operator: why was it difficult to implement?

由 谁说胖子不能爱 提交于 2019-12-01 15:03:09
I watched the Oracle OTN Virtual Event: Java SE and JavaFX 2.0 (28 Feb 2012) and while talking about the new diamond operator (that Map<String, List<String>> myMap = new HashMap<>(); thing) the speaker mentioned that it was not as simpleto implement than one might think, as it is not a simple token replacement. My question is why? Why can't be this implemented as simply taking the string from the variable's declaration and put it into the diamond operator? I didn't implement it either, so I can only guess. But usually the reason these things are more complex than they seem is that first
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