Java Cheat Sheet : Java Glossary

I have most of these common patterns built-in as SlickEdit macros so I don’t have to remember the patterns. I just click a custom icon for the pattern I want. Unfortunately, I thus don’t remember them. Without my editor, I would be at a loss to remember where the parentheses and semicolons go.

Control Structures

Loops

Try/Catch/Throw

Try/Catch/Finally

Literals

• int

  1, -1, hex ints 0x0f28, Unicode hex '\u003f', octal 027, Integer.MAX_VALUE (2,147,483,647), Integer.MIN_VALUE (-2,147,483,648) Beware! A lead 0 on an integer e.g. 007 implies OCTAL. That was a major design blunder inherited from C, guaranteed to introduce puzzling bugs. Be especially careful when specifying months or days, where you naturally tend to provide a lead 0.

• byte / short

  There is no such thing as a byte or short literal. You would have to write it with a cast e.g. (byte)0xff or (short)-99.

• long

  3L, -99l, 0xf011223344L, Long.MAX_VALUE (9,223,372,036,854,775,807), Long.MIN_VALUE (-9,223,372,036,854,775,808). Beware! some compilers will quietly chop the high bits from literals that don’t have a trailing L even when assigning to a long.

• float

  1.0345F, 1.04E-12f, .0345f, 1.04e-13f, Float.NaN.

• double

  5.6E-120D, 123.4d, 0.1, Double.NaN, Math.PI.
  Note floating point literals without the explicit trailing f, F, d or D are considered double. In theory you don’t need a lead 0, e.g. 0.1d may be written .1d, though the Solaris and Symantec compilers seem to require it. With floats and double, the lead zero does not mean octal

• boolean

  true and false.

• String

  // splitting a string literal over more than one line
  
  String s = "abcdefghijklmnopqrst"
            + "uvwxyz";

  There is no speed penalty for the + concatenation. It is done at compile time. String literals can be used anywhere you might use a String reference. e.g. "abc".charAt(1) is legal. For problematic/awkward/reserved/quotable characters like embedded ", see escape sequences below.

• char

  'A', enclosed in single quotes, or integer forms e.g. ( char)45, ( char)0x45, '\u003f'. For problematic characters like embedded ', see escape sequences below.

• Escape sequences

  inside char and String literals include:
  ' ' space
  '\u003f' Unicode hex, (must be exactly 4 digits to give a 16-bit Unicode number ). \u2007 is Figure Space, a space as wide as a digit, to help in aligning numbers.
  '\n' newline, ctrl-J (10, x0A)
  '\b' backspace, ctrl-H (8, 0x08)
  '\f' formfeed, ctrl-L (12, 0x0C)
  '\r' carriage return, ctrl-M (13, 0x0D)
  '\t' tab, ctrl-I (9, 0x09)
  '\\' backslash,
  '\'' single quote (optional inside " "),
  '\"' double quote (optional inside ' '),
  '\377' octal (must be exactly 3 digits. You can get away with fewer, but then you create an ambiguity if the character following the literal just happens to be in the range 0..7.). This lets you get at only the 8-bit characters in the range 0..377 octal or 0..255 decimal or 0..255 decimal, which still gives you 16-bit Unicode.
  \007 bel, ctrl-G (7, 0x07)
  \010 backspace, ctrl-H (8, 0x08)
  \013 vt vertical tab, ctrl-K (11, 0x0B)
  \032 sub (used in DOS/CPM as eof), ctrl-Z (26, 0x1A)
  \033 esc ctrl-^ (27, 0x1B)
• Unsupported
  There is no Pascalian '#nnn' style way of specifying decimal constants. Just use char c = 123;
  The following C forms are not supported: '\a' alert
  '\v' vertical tab
  '\?' question mark
  '\xf2' hex. Use the Unicode \uffff form for printable characters.

Primitives

Primitives vs Immutable Wrapper Objects

Precedence

// Be very careful reusing a pre or post increment variable in an expression.
int x = 2;
int y = x++ * ++x;  // result is y = 8;

// it works as if you had coded:
int x = 2;
int a = x++;   // a=2; x=3;
int b = ++x;   // b=4; x=4
int y = a * b; // y = 8

false ^ false == false
false ^ true == true
true ^ false == true
true ^ true == false

long encrypted = message ^ scrambler;
long decryped = encrypted ^ scrambler;

int e = ( a & b << 2 ) | ( c & ( d >>> 1 ) );
// if you trust precedence can be written more tersely:
int e = a & b << 2 | c & d >>> 1;

if ( ( ( lowest <= a ) && ( a <= biggest ) ) || notNeeded )

if ( lowest <= a && a <= biggest || notNeeded )

Keywords

Javadoc