Java Random doubles() Method

The doubles() method of Random class returns a stream of pseudorandom double values, each conforming between zero and one.
The second syntax effectively returns an unlimited stream of pseudorandom double values, each conforming to the given randomNumberOrigin and randomNumberBound.
The third syntax returns a stream producing the pseudorandom double values for the given streamSize number, each between zero and one.
The last syntax returns a stream producing the given streamSizenumber of pseudorandom double values, each conforming to the given origin and bound.

Syntax

public DoubleStream doubles()
public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound)
public DoubleStream doubles(long streamSize)
public DoubleStream doubles(long streamSize, double randomNumberOrigin, double randomNumberBound)

Parameter

streamSize- the number of values to generate

randomNumberOrigin- the origin of each random value

randomNumberBound- the bound of each random value

Return Value

The doubles() method returns :

a stream containing pseudorandom double values.
a stream containing pseudorandom double values, each having an origin and bound.
a stream containing double values.
a stream containing pseudorandom double values, each having an origin and bound.

Throws

IllegalArgumentException: if streamSize is a negative value.

IllegalArgumentException: if randomNumberOrigin is greater than or equal to randomNumberBound.

Example 1

import java.util.Random;

public class JavaRandomDoublesExample1 {
public static void main(String[] args) {
//create random object
Random random= new Random();
// will return a pseudorandom double value btw zero and one
for (int i=1;i<5;i++) {
System.out.println(i+". "+random.doubles());
        }
    }
}

Output:

1. [email protected]
2. [email protected]
3. [email protected]
4. [email protected]

Example 2

import java.util.Random;
import java.util.stream.DoubleStream;

public class JavaRandomDoublesExample2 {
static int i=1;
public static void main(String[] args) {
double randomNumberOrigin = 1;
double randomNumberBound = 7;
        Random random = new Random();
/*returns a stream of pseudorandom double value
        conforming to the given origin and bound */
DoubleStream d1 = random.doubles(randomNumberOrigin, randomNumberBound);
System.out.println(i + ". " + d1);
    }
}

Output:

1. [email protected]

Example 3

import java.util.Random;
import java.util.stream.DoubleStream;

public class JavaRandomDoublesExample3 {
public static void main(String[] args) {
double randomNumberOrigin=1;
//bound must be greater than origin
double randomNumberBound=1;
        Random random=new Random();
/*returns a stream of pseudorandom double value
        conforming to the given origin and bound */
DoubleStream d1=random.doubles(randomNumberOrigin,randomNumberBound);
System.out.println(d1);
    }
}

Output:

Exception in thread "main" java.lang.IllegalArgumentException: bound must be greater than origin
	atjava.util.Random.doubles(Random.java:983)
	at com.javaTpoint.JavaRandomDoublesExample3.main(JavaRandomDoublesExample3.java:14)

If randonNumberOrigin is greater than or equal to randomNumberBound, it will always give you the above-described runtime error, i.e., IllegalArgumentException.

Example 4

import java.util.Random;
import java.util.stream.DoubleStream;

public class JavaRandomDoublesExample4 {
static int i=1;
public static void main(String[] args) {
double randomNumberOrigin=1;
double randomNumberBound=7;
long streamSize=12358;
         Random random=new Random();
DoubleStream d1=random.doubles(randomNumberOrigin,randomNumberBound);
/*returns a stream producing given streamsize number
        of pseudorandom double value*/
DoubleStream d2 =random.doubles(streamSize);
/*returns a stream producing given streamsize number
        of pseudorandom double value, each between the given origin
        and bound*/
DoubleStream d3 =random.doubles(streamSize,randomNumberOrigin,randomNumberBound);
System.out.println(i+". "+d1);
System.out.println(i+1 +". "+d2);
System.out.println(i+2+". "+d3);
        }
}

Output:

1. [email protected]
2. [email protected]
3. [email protected]

Example 5

import java.util.Random;
import java.util.stream.DoubleStream;

public class JavaRandomDoublesExample5 {
public static void main(String[] args) {
double randomNumberOrigin=1;
double randomNumberBound=12;
//size must be non-negative
long streamSize=-1;
        Random random=new Random();
DoubleStream d1=random.doubles(randomNumberOrigin,randomNumberBound);
DoubleStream d2 =random.doubles(streamSize);
DoubleStream d3 =random.doubles(streamSize,randomNumberOrigin,randomNumberBound);
System.out.println(d1);
System.out.println(d2);
System.out.println(d3);
System.out.println(Math.random());

    }
}

Output:

Exception in thread "main" java.lang.IllegalArgumentException: size must be non-negative
	atjava.util.Random.doubles(Random.java:887)
	at com.javaTpoint.JavaRandomDoublesExample5.main(JavaRandomDoublesExample5.java:14)

If streamSize is less than zero, it will give you IllegalArgumentException, as described above.

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