Comparison to Java

Some Java issues addressed in Kotlin

Kotlin fixes a series of issues that Java suffers from

• Null references are controlled by the type system.
• No raw types
• Arrays in Kotlin are invariant
• Kotlin has proper function types, as opposed to Java's SAM-conversions
• Use-site variance without wildcards
• Kotlin does not have checked exceptions

What Java has that Kotlin does not

• Checked exceptions
• Primitive types that are not classes
• Static members
• Non-private fields
• Wildcard-types

What Kotlin has that Java does not

• Lambda expressions + Inline functions = performant custom control structures
• Extension functions
• Null-safety
• Smart casts
• String templates
• Properties
• Primary constructors
• First-class delegation
• Type inference for variable and property types
• Singletons
• Declaration-site variance & Type projections
• Range expressions
• Operator overloading
• Companion objects
• Data classes
• Separate interfaces for read-only and mutable collections