如何将所有双精度值更改为随机数?爪哇

问题描述

我想知道如何将所有50个双精度变量更改为随机数?

I was wondering how do I change all 50 double variables into random numbers?

class Main {
 public static void main(String[] args) {
     double[] numList = new double[50];

 }
}

推荐答案

Arrays#setAll

引用Javadoc:

Arrays#setAll

To quote the Javadoc:

i->Math.random()部分提供了我们的生成器功能.

The i -> Math.random() part is providing our generator function.

import java.util.Arrays;

public class Main {
    public static void main(String[] args) {
        double[] numList = new double[50];
        Arrays.setAll(numList, i -> Math.random());
        System.out.println(Arrays.toString(numList));
    }
}

示例运行的输出:

或者，

import java.util.Arrays;
import java.util.stream.IntStream;

public class Main {
    public static void main(String[] args) {
        double[] numList = IntStream.range(0, 50)
                    .mapToDouble(i -> Math.random()).toArray();
        System.out.println(Arrays.toString(numList));
    }
}

或者，

import java.util.Arrays;
import java.util.Random;

public class Main {
    public static void main(String[] args) {
        double[] array = new Random().doubles(50).toArray();
        System.out.println(Arrays.toString(array));
    }
}

或者，

import java.util.Arrays;
import java.util.concurrent.ThreadLocalRandom;

public class Main {
    public static void main(String[] args) {
        double[] array = ThreadLocalRandom.current().doubles(50).toArray();
        System.out.println(Arrays.toString(array));
    }
}

或者，

import java.util.Arrays;
import java.util.concurrent.ThreadLocalRandom;

public class Main {
    public static void main(String[] args) {
        final int SIZE = 50;
        double[] array = new double[SIZE];

        for (int i = 0; i < SIZE; i++) {
            array[i] = ThreadLocalRandom.current().nextDouble();
        }

        System.out.println(Arrays.toString(array));
    }
}

或者，

import java.util.Arrays;
import java.util.stream.Stream;

public class Main {
    public static void main(String[] args) {
        Double[] array = Stream.generate(Math::random).limit(50).toArray(Double[]::new);
        System.out.println(Arrays.toString(array));
    }
}

或者，

import java.util.Arrays;
import java.util.stream.Stream;

public class Main {
    public static void main(String[] args) {
        double[] array = Stream.generate(Math::random).limit(50).mapToDouble(Double::valueOf).toArray();
        System.out.println(Arrays.toString(array));
    }
}

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