Magic numbers are not readable

for (int i = 1; i =< 52; i++) {

j  =  i + randomInt(53 - i) – 1

swapEntries(i, j)

}

Replace with constants.

final int DECKSIZE = 52;

for (int i = 1; i =< DECKSIZE; i++) {

j  =  i + randomInt(DECKSIZE + 1 - i) – 1

swapEntries(i, j)

}

Implementation inheritance is difficult to debug.

Ask yourself: “Is this a kind of…?”

Alternatives:

Prefer interface inheritance.

Prefer composition over inheritance.

Binary numbers cannot exactly represent decimals.

Use BigDecimal for currency calculations.

...using the constructor that takes a String as a parameter.

If a variable need not be shared across methods, make it local.

private int x;

int method() {

x = 0;    // if you forget to initialize, you're dead

...         // do some stuff

return x;

}

int method() {

int x = 0;

...         // do some stuff

return x;

}

Every time you need to make a change in the routine, you need to edit it in several places. 

Don’t copy-paste code!

While there's no silver bullet for detecting this error, you can easily train yourself to make less of them. There's a very simple trick you can learn :-

all methods and member variables in the Java API begin with lowercase letters

all methods and member variables use capitalization where a new word begins e.g - getDoubleValue()

While there's no silver bullet for detecting this error, you can easily train yourself to make less of them. There's a very simple trick you can learn :-

all methods and member variables in the Java API begin with lowercase letters

all methods and member variables use capitalization where a new word begins e.g - getDoubleValue()

If you've come from a C/C++ background, you may not find this quite as much a problem as those who have used other languages. In Java, arrays are zero-indexed, meaning that the first element's index is actually 0