Para quem queria usar números binários em constantes, ou então separar os dígitos de 3 em 3 para facilitar a compreensão, o JDK 7 terá suporte a esse tipo de números.
Por exemplo, você pode escrever:
// números com underscores
double pi = 3.141_592_653_589_793_238_462_643_383_279_5;
// números binários - use 0B ou 0b
int cafebabe = 0b1100_1010_1111_1110_1011_1010_1011_1110;Este é o programa de teste do JDK 7.
public class UnderscoreLiterals {
public static void main(String... args) throws Exception {
new UnderscoreLiterals().run();
}
public void run() throws Exception {
// decimal
test(1, 1);
test(10, 10);
test(1_0, 10);
test(1__0, 10);
test(1_0_0, 100);
test(1__0__0, 100);
test(123_456_789, 123456789);
// long
test(1l, 1l);
test(10l, 10l);
test(1_0l, 10l);
test(1__0l, 10l);
test(1_0_0l, 100l);
test(1__0__0l, 100l);
test(123_456_789l, 123456789l);
// float
test(.1f, .1f);
test(.10f, .10f);
test(.1_0f, .10f);
test(.1__0f, .10f);
test(.1_0_0f, .100f);
test(.1__0__0f, .100f);
test(1e1, 1e1);
test(1e10, 1e10);
test(1e1_0, 1e10);
test(1e1__0, 1e10);
test(1e1_0_0, 1e100);
test(1e1__0__0, 1e100);
test(.123_456_789f, .123456789f);
test(0.1f, 0.1f);
test(0.10f, 0.10f);
test(0.1_0f, 0.10f);
test(0.1__0f, 0.10f);
test(0.1_0_0f, 0.100f);
test(0.1__0__0f, 0.100f);
test(0.123_456_789f, 0.123456789f);
test(1_1.1f, 1_1.1f);
test(1_1.10f, 1_1.10f);
test(1_1.1_0f, 1_1.10f);
test(1_1.1__0f, 1_1.10f);
test(1_1.1_0_0f, 1_1.100f);
test(1_1.1__0__0f, 1_1.100f);
test(1_1.123_456_789f, 1_1.123456789f);
// double
test(.1d, .1d);
test(.10d, .10d);
test(.1_0d, .10d);
test(.1__0d, .10d);
test(.1_0_0d, .100d);
test(.1__0__0d, .100d);
test(1e1, 1e1);
test(1e10, 1e10);
test(1e1_0, 1e10);
test(1e1__0, 1e10);
test(1e1_0_0, 1e100);
test(1e1__0__0, 1e100);
test(.123_456_789d, .123456789d);
test(0.1d, 0.1d);
test(0.10d, 0.10d);
test(0.1_0d, 0.10d);
test(0.1__0d, 0.10d);
test(0.1_0_0d, 0.100d);
test(0.1__0__0d, 0.100d);
test(0.123_456_789d, 0.123456789d);
test(1_1.1d, 1_1.1d);
test(1_1.10d, 1_1.10d);
test(1_1.1_0d, 1_1.10d);
test(1_1.1__0d, 1_1.10d);
test(1_1.1_0_0d, 1_1.100d);
test(1_1.1__0__0d, 1_1.100d);
test(1_1.123_456_789d, 1_1.123456789d);
// binary
test(0b1, 1);
test(0b10, 2);
test(0b1_0, 2);
test(0b1__0, 2);
test(0b1_0_0, 4);
test(0b1__0__0, 4);
test(0b0001_0010_0011, 0x123);
// octal
test(01, 1);
test(010, 8);
test(01_0, 8);
test(01__0, 8);
test(01_0_0, 64);
test(01__0__0, 64);
test(0_1, 1);
test(0_10, 8);
test(0_1_0, 8);
test(0_1__0, 8);
test(0_1_0_0, 64);
test(0_1__0__0, 64);
test(0_001_002_003, 01002003);
// hexadecimal
test(0x1, 1);
test(0x10, 16);
test(0x1_0, 16);
test(0x1__0, 16);
test(0x1_0_0, 256);
test(0x1__0__0, 256);
test(0x01_02_03_04, 0x1020304);
// misc
long creditCardNumber = 1234_5678_9012_3456L;
test(creditCardNumber, 1234567890123456L);
long socialSecurityNumbers = 999_99_9999L;
test(socialSecurityNumbers, 999999999L);
double monetaryAmount = 12_345_132.12d;
test(monetaryAmount, 12345132.12d);
long hexBytes = 0xFF_EC_DE_5E;
test(hexBytes, 0xffecde5e);
long hexWords = 0xFFEC_DE5E;
test(hexWords, 0xffecde5e);
long maxLong = 0x7fff_ffff_ffff_ffffL;
test(maxLong, 0x7fffffffffffffffL);
long maxLongDecimal = 9223372036854775807L;
long alsoMaxLong = 9_223_372_036_854_775_807L;
test(alsoMaxLong, maxLongDecimal);
double whyWouldYouEverDoThis = 0x1.ffff_ffff_ffff_fp10_23;
double whyWouldYouEverDoEvenThis = 0x1.fffffffffffffp1023;
test(whyWouldYouEverDoThis, whyWouldYouEverDoEvenThis);
if (errors > 0)
throw new Exception(errors + " errors found");
}
void test(int value, int expect) {
count++;
if (value != expect)
error("test " + count + "\nexpected: 0x" + Integer.toHexString(expect) + "\n found: 0x" + Integer.toHexString(value));
}
void test(double value, double expect) {
count++;
if (value != expect)
error("test " + count + "\nexpected: 0x" + expect + "\n found: 0x" + value);
}
void test(long value, long expect) {
count++;
if (value != expect)
error("test " + count + "\nexpected: 0x" + Long.toHexString(expect) + "\n found: 0x" + Long.toHexString(value));
}
void error(String message) {
System.out.println(message);
errors++;
}
int count;
int errors;
}