\u2022Objects & Variables
\n-Local var resides in stack -> space is allocated at method call and deallocated at method return<\/p>\n
-Objects are created on heap by the “new” operator but object ref is a value and resides in stack
\n-Objects in heap exist if reachable from some variable on stack. Otherwise they are GCed<\/p>\n
-Primitive types define values
\n-Nonprimitive types define objects<\/p>\n
-Primitive var contain values in stack
\n-Nonprimitive var contain reference values in stack pointing to objects in heap<\/p>\n
-object var assignment causes vars to share objects
\n-the “==” determines whether two vars contain same primitive value or same object ref value(points to same object in heap)
\n-prefer getClass in equals()<\/p>\n
-All objects are either mutable (e.g. Arrays) or immutable(e.g. Strings)<\/p>\n
\u2022Type Safety
\n-Java is a strong typed language
\n-Java provides automatic storage management for all objects
\n-Java checks all array accesses to ensure they are within bounds<\/p>\n
\u2022Type Hierarchy
\n-Apparent type vs Actual type<\/p>\n
\u2022Conversion and Overloading
\n-most specific rule for overloading otherwise error<\/p>\n
\u2022Exceptions
\nThrowable
\n\t<- Error\n\t\t<-VirtualMachineError\n\t\t <-OutOfMemoryError\n\t<- Exception\n\t\t<- RuntimeException\n\t\t\t<- unchecked excptns\n\t\t<- checked exceptions\n-Exceptions are not just errors. They also fulfills defensive programming\n\n-Use unchecked exception only if you expect that users will usually write code that ensures the exception will not happen because a)there is a convenient and inexpensive way to avoid exception b)the context of use is local\n\n\u2022Use chained exceptions to \n-abstract out low level exceptions;\n-decouple client from impl\n\n\u2022Load properties\nProperties p = new Properties();\np.load(\"app.properties\");\nString val = p.getProperty(\"name\");\n\n\u2022Use bundle\nPropertyResourceBundle bundle = (PropertyResourceBundle) ResourceBundle.getBundle(\"r1\");\n\n-In war\nInputStream is = \n this.getClass()\n .getClassLoader()\n .getResourceAsStream(\"pkg\/file\");\n\nor this.getClass().getResourceAsStream(\"pkg\/file\");\n\nor ClassLoader.get...\n\n\u2022Enable https support with URLclass\nSystem.setProperty(\"java.protocol.handler.pkqs\",\"com.sun.net.ssl.internal.www.protocol\");\njava.security.Security.addProvider( new com.sun.net.ssl.internal.ssl.Provider());\n\n\u2022Class types\nInteger.TYPE.getName()\n-Arrays\n[Ljava.lang.String\t\tString array\n[C\t\t\t\t\tchar array\n[Z\t\t\t\t\tboolen array\n[J\t\t\t\t\tlong array\n\n\n\n<\/p>\n","protected":false},"excerpt":{"rendered":"
\u2022Objects & Variables -Local var resides in stack -> space is allocated at method call and deallocated at method return -Objects are created on heap by the “new” operator but object ref is a value and resides in stack -Objects … Continue reading