Integer/Long constructor is inefficient, use valueOf instead JAVA-S0067
Performance
Major
Using Integer's default constructor is guaranteed to always result in a new object whereas Integer.valueOf allows the compiler/class library/JVM to cache values, which is known as interning.
Use of cached values avoids object allocation and the resulting code will be faster. Values between -128 and 127 are guaranteed to have corresponding cached instances and using valueOf is approximately 3.5 times faster than using the constructor. For values outside the constant range the performance of both styles is the same.
Examples
Problematic Code
Integer a = new Integer(34);
Recommended
Integer a = Integer.valueOf(34);
// or
Integer b = 34; // Autoboxing
Unless the class must be compatible with JVMs predating Java 1.5, use either autoboxing or the valueOf method when creating instances of Long, Integer, Short, Character, and Byte.
Note - This issue will be ignored within tests.
References
- Spotbugs - DM_NUMBER_CTOR