Java Number & Math

Java Number

byteintlongdouble

int a = 5000; float b = 13.65f; byte c = 0x4a;

Java

IntegerLongByteDoubleFloatShort Number


Byte	byte
Short	short
Integer	int
Long	long
Float	float
Double	double
BigInteger	-
BigDecimal	-

[Java Number]

Number java.lang

Number

public abstract class Number implements Serializable {
//
public abstract int intValue();
public abstract long longValue();
public abstract float floatValue();
public abstract double doubleValue();

// Java 8
public byte byteValue() {
return (byte)intValue();
}
public short shortValue() {
return (short)intValue();
}
}

Integer

Test.java

public class Test{ public static void main(String[] args){ Integer x = 5; x = x + 10; System.out.println(x); } }

x xxxx

Number num = 1234.56; // Double

System.out.println(num.intValue()); // 1234 ()
System.out.println(num.longValue()); // 1234
System.out.println(num.floatValue()); // 1234.56
System.out.println(num.doubleValue()); // 1234.56

java
Integer x = 10;
Double y = 10.0;

//
System.out.println(x.doubleValue() == y.doubleValue()); // true

BigInteger bigInt = new BigInteger("12345678901234567890");
BigDecimal bigDec = new BigDecimal("1234567890.1234567890");

//
BigInteger sum = bigInt.add(new BigInteger("1"));
BigDecimal product = bigDec.multiply(new BigDecimal("2"));

NumberFormat nf = NumberFormat.getInstance();
nf.setMaximumFractionDigits(2);

System.out.println(nf.format(1234.5678)); // "1,234.57"

Java 5+

//
Integer autoBoxed = 42; // Integer.valueOf(42)

//
int autoUnboxed = autoBoxed; // autoBoxed.intValue()

Java Math

Math Java java.lang

Java Math

Math static Math

Test.java

public class Test { public static void main (String []args) { System.out.println("90 " + Math.sin(Math.PI/2)); System.out.println("0" + Math.cos(0)); System.out.println("60" + Math.tan(Math.PI/3)); System.out.println("1 " + Math.atan(1)); System.out.println("/2" + Math.toDegrees(Math.PI/2)); System.out.println(Math.PI); } }

90 1.0
01.0
601.7320508075688767
1 0.7853981633974483
π/290.0
3.141592653589793

1.

Math.exp(1); // e^1 2.718
Math.log(Math.E); // ln(e) = 1
Math.log10(100); // log10(100) = 2

2.

// [0.0, 1.0)
double random = Math.random();

// [1, 100]
int randomInt = (int)(Math.random() * 100) + 1;

3.

Math.hypot(3, 4); // sqrt(x+y) 5.0
Math.IEEEremainder(10, 3); // IEEE 1.0

4.

Math.PI; // 3.141592653589793
Math.E; // e 2.718281828459045

Number & Math


1	xxxValue() Number xxx
2	compareTo() number
3	equals() number
4	valueOf() Number
5	toString()
6	parseInt() int
7	abs()
8	ceil() ( >= )
9	floor() <=
10	rint() double
11	round() Math.floor(x+0.5) 0.5 Math.round(11.5) 12Math.round(-11.5) -11
12	min()
13	max()
14	exp() e
15	log()
16	pow()
17	sqrt()
18	sin() double
19	cos() double
20	tan() double
21	asin() double
22	acos() double
23	atan() double
24	atan2()
25	toDegrees()
26	toRadians()
27	random()

Math floor,round ceil

	Math.floor	Math.round	Math.ceil
1.4	1	1	2
1.5	1	2	2
1.6	1	2	2
-1.4	-2	-1	-1
-1.5	-2	-1	-1
-1.6	-2	-2	-1

floor,round ceil

public class Main { public static void main(String[] args) { double[] nums = { 1.4, 1.5, 1.6, -1.4, -1.5, -1.6 }; for (double num : nums) { test(num); } } private static void test(double num) { System.out.println("Math.floor(" + num + ")=" + Math.floor(num)); System.out.println("Math.round(" + num + ")=" + Math.round(num)); System.out.println("Math.ceil(" + num + ")=" + Math.ceil(num)); } }

Math.floor(1.4)=1.0
Math.round(1.4)=1
Math.ceil(1.4)=2.0
Math.floor(1.5)=1.0
Math.round(1.5)=2
Math.ceil(1.5)=2.0
Math.floor(1.6)=1.0
Math.round(1.6)=2
Math.ceil(1.6)=2.0
Math.floor(-1.4)=-2.0
Math.round(-1.4)=-1
Math.ceil(-1.4)=-1.0
Math.floor(-1.5)=-2.0
Math.round(-1.5)=-1
Math.ceil(-1.5)=-1.0
Math.floor(-1.6)=-2.0
Math.round(-1.6)=-2
Math.ceil(-1.6)=-1.0

/** * @author Dale * java * */ public class Number { public static void main(String[] args) { /** Integer i1 = 128; // Integer.valueOf(128); int t = i1; // i1.intValue() System.out.println(t); */ /** –128127127, ,new */ Integer i1 = 200; Integer i2 = 200; /** == equals == equals */ if(i1==i2) { System.out.println("true"); } else { System.out.println("false"); } } }

/** * newIntegernewInteger */ public class Test { public static void main(String[] args) { Integer i= new Integer(200); Integer j = 200; System.out.print(i == j); //false } }

/** * newInteger */ public class Test { public static void main(String[] args) { Integer i1 = 127; Integer ji = 127; System.out.println(i1 == ji);//true Integer i2 = 128; Integer j2 = 128; System.out.println(i2 == j2);//false } }

/** * Integerint */ public class Test { public static void main(String[] args) { Integer i1 = 200; Integer i2 = new Integer(200); int j = 200; System.out.println(i1 == j);//true System.out.println(i2 == j);//true } }

100

x10 (2017-03-23)

128

1Java -128 ~ 127 -128 ~ 127

Integer a=123;
Integer b=123;
System.out.println(a==b);        //  true
System.out.println(a.equals(b));  //  true

2 Integer -128 ~ 127 ,

a=1230;
b=1230;
System.out.println(a==b);        //  false
System.out.println(a.equals(b));  //  true

estivalwind8 (2018-07-21)

210

Java int Integer

1. int int Integer Integer

Integer i = new Integer(100);
Integer j = new Integer(100);
System.out.print(i == j); //false

new

int Integer

Integer Integer int

4. new Integer new Integer() false

new Integer java new Integer() false

5. new Integer [-128,127] true false

java Integer i1 = 127 Integer i1 = Integer.valueOf(127)

6. Integer ( new ) int true

Integer int Integer int int true

flaming8 (2018-12-12)

Math.floor

Math.ceil

Math.round

1 5
2 5 +1
3 5 +1

yuki7 (2019-04-25)

byteintlongdouble java

Integer i = 1000;
double p =  Math.random() + i;
Double q =  Math.random() + i;
System.out.println(p);

JavaNewer7 (2019-05-14)

floor()ceil()

1. floor

2. ceilceiling

floor()ceil()double

round()y

inytialf7 (2020-01-11)

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Java

Java

Java Number & Math

Java Number

Test.java

Java Math

Test.java

1.

2.

3.

4.

Number & Math

Math floor,round ceil

floor,round ceil

6