Class GenericWhitespaceCheck

Checks that the whitespace around the Generic tokens (angle brackets) "<" and ">" are correct to the typical convention. The convention is not configurable.

Left angle bracket ("<"):

• should be preceded with whitespace only in generic methods definitions.
• should not be preceded with whitespace when it is precede method name or constructor.
• should not be preceded with whitespace when following type name.
• should not be followed with whitespace in all cases.

Right angle bracket (">"):

• should not be preceded with whitespace in all cases.
• should be followed with whitespace in almost all cases, except diamond operators and when preceding method name or constructor.

To configure the check:

 <module name="GenericWhitespace"/>
 

Examples with correct spacing:

 // Generic methods definitions
 public void <K, V extends Number> boolean foo(K, V) {}
 // Generic type definition
 class name<T1, T2, ..., Tn> {}
 // Generic type reference
 OrderedPair<String, Box<Integer>> p;
 // Generic preceded method name
 boolean same = Util.<Integer, String>compare(p1, p2);
 // Diamond operator
 Pair<Integer, String> p1 = new Pair<>(1, "apple");
 // Method reference
 List<T> list = ImmutableList.Builder<T>::new;
 // Method reference
 sort(list, Comparable::<String>compareTo);
 // Constructor call
 MyClass obj = new <String>MyClass();
 

Examples with incorrect spacing:

 List< String> l; // violation, "<" followed by whitespace
 Box b = Box. <String>of("foo"); // violation, "<" preceded with whitespace
 public<T> void foo() {} // violation, "<" not preceded with whitespace

 List a = new ArrayList<> (); // violation, ">" followed by whitespace
 Map<Integer, String>m; // violation, ">" not followed by whitespace
 Pair<Integer, Integer > p; // violation, ">" preceded with whitespace
 

Parent is com.puppycrawl.tools.checkstyle.TreeWalker

Violation Message Keys:

• ws.followed
• ws.illegalFollow
• ws.notPreceded
• ws.preceded