深入学习java源码之Math.addExact()与 Math.multiplyExact()
2024-06-04 07:31:24
深入学习java源码之Math.addExact()与 Math.multiplyExact()
^运算符
或的运算符，其运算规则是：
两个操作数的位中，相同则结果为0，不同则结果为1。
int i = 15, j = 2
运行结果是：i ^ j = 13.
分析上面程序，i=15转成二进制是1111，j=2转成二进制是0010，根据异或的运算规则得到的是1101，转成十进制就是13.
K+1个数，其中有2k个相同，需要找出不相同的那个数，比如：2、3、4、4、3、5、6、6、5。
int[] array = {2,3,4,4,3,5,6,6,5};int v = 0;for (int i = 0;i < array.length;i++) {v ^= array[i];System.out.println("只出现一次的数是:" + v);}只出现一次的数是2.基本数据类型的加减乘除运算
加法
int a = 10;long b = 35;float c = 36.95f;double d = 18.04;减法
long a = 300;
int b = 18;
float c = 128.7f;
double d = 53.31;float jian = (float)(a - b - c - (double)d);乘法
int a = 1;
long b = 1000000;
float c = 0.000001f;
double d = 99.99;除法
int a = 1000;
long b = 1000000;
float c = 0.001f;
double d = 99.99;float chu = (float)((double)d/(a/b/c));| Modifier and Type | Method and Description |
|---|---|
static double
|
abs(double a)
返回值为 |
static float
|
abs(float a)
返回 |
static int
|
abs(int a)
返回值为 |
static long
|
abs(long a)
返回值为 |
static int
|
addExact(int x, int y)
返回其参数的总和，如果结果溢出int，则抛出 |
static long
|
addExact(long x, long y)
返回其参数的总和，如果结果溢出long，则抛出 |
static int
|
decrementExact(int a)
返回一个递减1的参数，如果结果溢出int，则 |
static long
|
decrementExact(long a)
将返回的参数递减1，如果结果溢出long，则 |
static double
|
floor(double a)
返回小于或等于参数的最大（最接近正无穷大） |
static int
|
floorDiv(int x, int y)
返回小于或等于代数商的最大（最接近正无穷大） |
static long
|
floorDiv(long x, long y)
返回小于或等于代数商的最大（最接近正无穷大） |
static int
|
floorMod(int x, int y)
返回 |
static long
|
floorMod(long x, long y)
返回 |
static int
|
incrementExact(int a)
返回自变量1，如果结果溢出int，则 |
static long
|
incrementExact(long a)
返回一个增加1的参数，如果结果溢出long，则 |
static int
|
multiplyExact(int x, int y)
返回参数的乘积，如果结果溢出int，则抛出 |
static long
|
multiplyExact(long x, long y)
返回参数的乘积，如果结果溢出long，则抛出 |
static int
|
negateExact(int a)
返回参数的否定，如果结果溢出int，则 |
static long
|
negateExact(long a)
返回参数的否定，如果结果溢出long，则 |
static long
|
round(double a)
返回参数中最接近的 |
static int
|
round(float a)
返回参数中最接近的 |
static int
|
subtractExact(int x, int y)
返回参数的差异，如果结果溢出int，则抛出 |
static long
|
subtractExact(long x, long y)
返回参数的差异，如果结果溢出long，则抛出 |
static int
|
toIntExact(long value)
返回 |
java源码
public final class Math {private Math() {}public static int round(float a) {int intBits = Float.floatToRawIntBits(a);int biasedExp = (intBits & FloatConsts.EXP_BIT_MASK)>> (FloatConsts.SIGNIFICAND_WIDTH - 1);int shift = (FloatConsts.SIGNIFICAND_WIDTH - 2+ FloatConsts.EXP_BIAS) - biasedExp;if ((shift & -32) == 0) { // shift >= 0 && shift < 32// a is a finite number such that pow(2,-32) <= ulp(a) < 1int r = ((intBits & FloatConsts.SIGNIF_BIT_MASK)| (FloatConsts.SIGNIF_BIT_MASK + 1));if (intBits < 0) {r = -r;}// In the comments below each Java expression evaluates to the value// the corresponding mathematical expression:// (r) evaluates to a / ulp(a)// (r >> shift) evaluates to floor(a * 2)// ((r >> shift) + 1) evaluates to floor((a + 1/2) * 2)// (((r >> shift) + 1) >> 1) evaluates to floor(a + 1/2)return ((r >> shift) + 1) >> 1;} else {// a is either// - a finite number with abs(a) < exp(2,FloatConsts.SIGNIFICAND_WIDTH-32) < 1/2// - a finite number with ulp(a) >= 1 and hence a is a mathematical integer// - an infinity or NaNreturn (int) a;}} public static long round(double a) {long longBits = Double.doubleToRawLongBits(a);long biasedExp = (longBits & DoubleConsts.EXP_BIT_MASK)>> (DoubleConsts.SIGNIFICAND_WIDTH - 1);long shift = (DoubleConsts.SIGNIFICAND_WIDTH - 2+ DoubleConsts.EXP_BIAS) - biasedExp;if ((shift & -64) == 0) { // shift >= 0 && shift < 64// a is a finite number such that pow(2,-64) <= ulp(a) < 1long r = ((longBits & DoubleConsts.SIGNIF_BIT_MASK)| (DoubleConsts.SIGNIF_BIT_MASK + 1));if (longBits < 0) {r = -r;}// In the comments below each Java expression evaluates to the value// the corresponding mathematical expression:// (r) evaluates to a / ulp(a)// (r >> shift) evaluates to floor(a * 2)// ((r >> shift) + 1) evaluates to floor((a + 1/2) * 2)// (((r >> shift) + 1) >> 1) evaluates to floor(a + 1/2)return ((r >> shift) + 1) >> 1;} else {// a is either// - a finite number with abs(a) < exp(2,DoubleConsts.SIGNIFICAND_WIDTH-64) < 1/2// - a finite number with ulp(a) >= 1 and hence a is a mathematical integer// - an infinity or NaNreturn (long) a;}}public static int addExact(int x, int y) {int r = x + y;// HD 2-12 Overflow iff both arguments have the opposite sign of the resultif (((x ^ r) & (y ^ r)) < 0) {throw new ArithmeticException("integer overflow");}return r;}public static long addExact(long x, long y) {long r = x + y;// HD 2-12 Overflow iff both arguments have the opposite sign of the resultif (((x ^ r) & (y ^ r)) < 0) {throw new ArithmeticException("long overflow");}return r;}public static int subtractExact(int x, int y) {int r = x - y;// HD 2-12 Overflow iff the arguments have different signs and// the sign of the result is different than the sign of xif (((x ^ y) & (x ^ r)) < 0) {throw new ArithmeticException("integer overflow");}return r;}public static long subtractExact(long x, long y) {long r = x - y;// HD 2-12 Overflow iff the arguments have different signs and// the sign of the result is different than the sign of xif (((x ^ y) & (x ^ r)) < 0) {throw new ArithmeticException("long overflow");}return r;}public static int multiplyExact(int x, int y) {long r = (long)x * (long)y;if ((int)r != r) {throw new ArithmeticException("integer overflow");}return (int)r;}public static long multiplyExact(long x, long y) {long r = x * y;long ax = Math.abs(x);long ay = Math.abs(y);if (((ax | ay) >>> 31 != 0)) {// Some bits greater than 2^31 that might cause overflow// Check the result using the divide operator// and check for the special case of Long.MIN_VALUE * -1if (((y != 0) && (r / y != x)) ||(x == Long.MIN_VALUE && y == -1)) {throw new ArithmeticException("long overflow");}}return r;}public static int incrementExact(int a) {if (a == Integer.MAX_VALUE) {throw new ArithmeticException("integer overflow");}return a + 1;}public static long incrementExact(long a) {if (a == Long.MAX_VALUE) {throw new ArithmeticException("long overflow");}return a + 1L;}public static int decrementExact(int a) {if (a == Integer.MIN_VALUE) {throw new ArithmeticException("integer overflow");}return a - 1;}public static long decrementExact(long a) {if (a == Long.MIN_VALUE) {throw new ArithmeticException("long overflow");}return a - 1L;}public static int negateExact(int a) {if (a == Integer.MIN_VALUE) {throw new ArithmeticException("integer overflow");}return -a;}public static long negateExact(long a) {if (a == Long.MIN_VALUE) {throw new ArithmeticException("long overflow");}return -a;}public static int toIntExact(long value) {if ((int)value != value) {throw new ArithmeticException("integer overflow");}return (int)value;} public static int abs(int a) {return (a < 0) ? -a : a;}public static long abs(long a) {return (a < 0) ? -a : a;}public static float abs(float a) {return (a <= 0.0F) ? 0.0F - a : a;}public static double abs(double a) {return (a <= 0.0D) ? 0.0D - a : a;} public static long floorDiv(long x, long y) {long r = x / y;// if the signs are different and modulo not zero, round downif ((x ^ y) < 0 && (r * y != x)) {r--;}return r;}public static int floorDiv(int x, int y) {int r = x / y;// if the signs are different and modulo not zero, round downif ((x ^ y) < 0 && (r * y != x)) {r--;}return r;}public static int floorMod(int x, int y) {int r = x - floorDiv(x, y) * y;return r;}public static long floorMod(long x, long y) {return x - floorDiv(x, y) * y;}} public final class StrictMath {private StrictMath() {}public static int round(float a) {return Math.round(a);}public static long round(double a) {return Math.round(a);}public static int addExact(int x, int y) {return Math.addExact(x, y);}public static long addExact(long x, long y) {return Math.addExact(x, y);}public static int subtractExact(int x, int y) {return Math.subtractExact(x, y);}public static long subtractExact(long x, long y) {return Math.subtractExact(x, y);}public static int multiplyExact(int x, int y) {return Math.multiplyExact(x, y);}public static long multiplyExact(long x, long y) {return Math.multiplyExact(x, y);}public static int toIntExact(long value) {return Math.toIntExact(value);}public static int floorDiv(int x, int y) {return Math.floorDiv(x, y);}public static long floorDiv(long x, long y) {return Math.floorDiv(x, y);}public static int floorMod(int x, int y) {return Math.floorMod(x , y);}public static long floorMod(long x, long y) {return Math.floorMod(x, y);}public static int abs(int a) {return Math.abs(a);}public static long abs(long a) {return Math.abs(a);}public static float abs(float a) {return Math.abs(a);}public static double abs(double a) {return Math.abs(a);}}深入学习java源码之Math.addExact()与 Math.multiplyExact()相关推荐
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