Breaking existing code

As of Java 10, var is a restricted local variable type and cannot be used for type declarations. Code that uses var as the name of a class, interface, method, method parameters, or variables, will no longer compile in JDK 10 and later releases.

The following is an example of code that uses var at multiple places and won't compile:

class var {}          // can't use var as class name
interface var {}      // can't use var as interface name
class Demo {
    int var = 100;               // can't use var as instance variable 
                                 // name
    static long var = 121;       // can't use var as static variable 
                                 // name

    void var() {                 // can't use var as method name
        int var = 10;            // cant use var as the name of a local 
                                 // variable
    }
    void aMethod(String var) {}  // can't use var as the name of method parameter
}