Java's type system provides programmers with strong guarantees of type and memory safety, but there are many important properties not captured by standard Java types. We describe JQual, a tool that adds user-defined type qualifiers to Java, allowing programmers to quickly and easily incorporate extra lightweight, application-specific type checking into their programs. JQual provides type qualifier inference, so that programmers need only add a few key qualifier annotations to their program, and then JQual infers any remaining qualifiers and checks their consistency. We explore two applications of JQual. First, we introduce opaque and enum qualifiers to track C pointers and enumerations that flow through Java code via the JNI. In our benchmarks we found that these C values are treated correctly, but there are some places where a client could potentially violate safety. Second, we introduce a readonly qualifier for annotating references that cannot be used to modify the objects they refer to. We found that JQual is able to automatically infer readonly in many places on method signatures. These results suggest that type qualifiers and type qualifier inference are a useful addition to Java.

We propose a data structure for d-dimensional simplicial complexes, that we call the Simplified Incidence Graph (SIG). The simplified incidence graph encodes all simplices of a simplicial complex together with a set of boundary and partial co-boundary topological relations. It is a dimension-independent data structure in the sense that it can represent objects of arbitrary dimensions. It scales well to the manifold case, i.e. it exhibits a small overhead when applied to simplicial complexes with a manifold domain. Here, we present efficient navigation algorithms for retrieving all topological relations from a SIG, and an algorithm for generating a SIG from a representation of the complex as an incidence graph. Finally, we compare the simplified incidence graph with the incidence graph, with a widely-used data structure for d-dimensional pseudo-manifold simplicial complexes, and with two data structures specific for two-and three-dimensional simplicial complexes.

Java's type system provides programmers with strong guarantees of type and memory safety, but there are many important properties not captured by standard Java types. We describe JQual, a tool that adds user-defined type qualifiers to Java, allowing programmers to quickly and easily incorporate extra lightweight, application-specific type checking into their programs. JQual provides type qualifier inference, so that programmers need only add a few key qualifier annotations to their program, and then JQual infers any remaining qualifiers and checks their consistency. We explore two applications of JQual. First, we introduce opaque and enum qualifiers to track C pointers and enumerations that flow through Java code via the JNI. In our benchmarks we found that these C values are treated correctly, but there are some places where a client could potentially violate safety. Second, we introduce a readonly qualifier for annotating references that cannot be used to modify the objects they refer to. We found that JQual is able to automatically infer readonly in many places on method signatures. These results suggest that type qualifiers and type qualifier inference are a useful addition to Java.

Type qualifiers are a lightweight, practical mechanism for specifying and checking program properties. In previous work, we have developed CQUAL, a tool for adding type qualifiers to C. In this short article, we describe an Eclipse plug-in for CQUAL that allows programmers to visualize the results of CQUAL's type qualifier inference and thereby quickly understand and resolve potential programming errors.