O

Object class

equals(), 524–529

hashCode(), 529–536

Java refresher, 2

methods, 523

object eligibility for garbage collection, 247

objects defined, 2

objects in heap memory, 174

thread-related methods, 690

toString(), 522–524

"object graph," serialization and, 445–449

object orientation

cohesion, 147, 149–150

constructor chaining, 128–129

constructor rules, 129–130

constructors, 126–128

coupling and cohesion, 147–149

default constructors, when created, 131–135

encapsulation, 82–85

HAS-A relationships, 92–94

inheritance, 86–90

interface implementation, 115–121

IS-A relationships, 90–91

object-oriented design, 93

overloaded constructors, 135–141

overloaded methods, 105–109

overridden methods, 99–105

polymorphism, 94–98, 109–111

reference variable casting, 112–115

return types, 122–126

self test answers, 164–172

self test questions, 158–163

statics, 141–147

two-minute drill, 153–155

object references

arrays of, 221

default values, 193

equality operators, 280

instance variables, 194–196

instanceof operator and, 283–285

local object references, 199–200

passing object reference variables, 203–204

ObjectInputStream, 444–445

ObjectOutputStream, 444–445

octal literals, 177

one-dimensional arrays

assigning, 222–223

constructing, 211–212

operators, 276–314

arithmetic, 286

assignment, 276–277

bitwise, 293

compound assignment, 277–278

conditional, 292–293

equality, 280–283

increment/decrement, 290–291

instanceof, 283–286

logical, 293, 296–298

operator precedence, 278

overview, 276

relational, 278–279

remainder (%), 287

self test answers, 307–314

self test questions, 301–306

short-circuit logical, 294–296

string concatenation, 287–289

two-minute drill, 299–303

OR ( | ) operator, 296–297

OR ( | | ) operator, short-circuit OR, 294–296

ordered collections, 540

outer classes

creating inner class from outside outer class, 640–642

creating inner class instance from outer class instance, 640–642

instantiating inner class from within, 640

referencing inner classes from, 639

overloaded constructors, 135–141

overloaded methods, 105–109

invoking, 107–109

legal overloads, 106

vs. overridden, 106, 111

polymorphism in, 109–111

rules for, 105–106

two-minute drill, 154

overloading, advanced

overloading combined with var-args, 243–244

overloading combined with widening and boxing, 242–243

overloading with boxing and var-args, 239–240

overloading with widening reference variables, 240–241

overview, 237–239

two-minute drill, 258

overridden methods, 99–105

equals(), 524–525

example, 99–101

hashCode(), 529–530

illegal, 110

legal and illegal examples of, 105

vs. overloaded, 106, 111

polymorphism in, 109–111

rules for overriding a method, 102–103

superclass versions of, 103–104

toString(), 522–524

two-minute drill, 154