@Override
    public long getPercentFree() {
        if (this.capacity == 0) {
            return 0;
        }
        return (this.capacity - this.size) * PERCENTAGE_VALUE / this.capacity;
    }
Simple implementation of cache statistics.

@author Marvin S. Addison
@since 3.5.1
core/cas-server-core-monitor/src/main/java/org/apereo/cas/monitor/SimpleCacheStatistics.java