java8 泛型声明 The diamond operator ("<>") should be used

Posted 2020-06-17

 

The diamond operator ("<>") should be used

Java 7 introduced the diamond operator (<>) to reduce the verbosity of generics code. For instance, instead of having to declare a List‘s type in both its declaration and its constructor, you can now simplify the constructor declaration with <>, and the compiler will infer the type.

Note that this rule is automatically disabled when the project‘s java.source.version is lower than 7.

Noncompliant Code Example

List<String> strings = new ArrayList<String>();  // Noncompliant
Map<String,List<Integer>> map = new HashMap<String,List<Integer>>();  // Noncompliant

Compliant Solution

List<String> strings = new ArrayList<>();
Map<String,List<Integer>> map = new HashMap<>();