将十进制数转换为二进制数并计算 1 的数量的Java程序

根据数字系统，默认计算是通过十进制数进行的，其基数标准化为 10。机器在 0 和 1 中计算物理层的所有执行。因此需要一个以 2 为基数的数字系统，称为二进制数字系统。二进制数可以转换为十进制数，反之亦然。在Java中有4种类型的数字：

Types Of Numbers	Base
Binary	2
Octa-Decimal	8
Decimal	10
Hexadecimal	16

方法：在Java中，有两种方法可以使用预定义方法或三级逻辑构建进行转换，如下所示：

1. 使用Integer.toBinaryString方法（整数包装类）
2. 使用蛮力方法（不使用任何预定义类）

例子：

Input. 1: 10
Output 1: The binary equivalent of 10 is : 1010
          Number of 1s is : 2

Input  2: 15
Output 2: The binary equivalent of 15 is : 1111
          Number of 1s is 4

方法一：使用toBinaryString()方法：表示要转换成二进制的数。 Java的 Integer 类提供了一些有用的方法来处理整数。一种这样的方法是Integer.toBinaryString(int x)  

句法：

public static String toBinaryString(int variable_name)

参数：要转换的十进制整数。

返回类型：字符串，它保存转换后的整数的二进制表示或作为 String 对象的整数的简单二进制等价物。

异常：此方法没有抛出异常

参数：它需要一个整数（或整数）类型的参数

实现：统计1的个数，检查得到的二进制字符串的每个字符是否等于1。

Java

// Java program to convert decimal to binary number
// and counting number of 1's in it
  
public class GFG {
  
    // Function to convert decimal to binary
    void convertAndCount(int num)
    {
        // Store the count of 1s currently 0
        int count = 0;
  
        // Returns a String object representing
        // binary equivalent of passed decimal number
        String binary = Integer.toBinaryString(num);
  
        // Iterating over obtained string using length
        // function
        for (int i = 0; i < binary.length(); i++)
  
            // Checking 1 is present in binary
            if (binary.charAt(i) == '1')
  
                // Increment the count
                // if any char equals 1
                count++;
  
        // Printing the binary equivalent
        System.out.println("The binary equivalent of " + num
                           + " is : " + binary);
  
        // Printing the no of 1 in above binary number
        System.out.println("Number of 1s is : " + count);
    }
  
    // Main driver method
    public static void main(String[] args)
    {
        // Creating object in main
        GFG obj = new GFG();
  
        // Calling the convertAndCount() method
        // over the integer value 18
        obj.convertAndCount(18);
    }
}

输出

The binary equivalent of 18 is : 10010
Number of 1s is : 2

方法二：不使用预定义变量

• 将十进制数除以 2 将转换为二进制数
• 存储剩余部分

Java

// Java program to convert decimal to binary number
// and counting number of 1's in it
  
public class GFG {
  
    // Function to convert decimal to binary
    void convertAndCount(int num)
    {
        int temp = num; // a temporary variable to store the
                        // value of num
  
        // to store the binary value
        int[] binary = new int[20];
  
        // to store the count of 1s
        int count = 0;
        int i;
  
        // to iterate through the loop and keep a
        // count of no.of digits in the obtained binary
        for (i = 0; temp > 0; i++) {
  
            // divide the number by 2
            // and store the remainder
            temp /= 2;
            binary[i] = temp % 2;
  
            // If 1 is present in binary
            if (binary[i] == 1)
  
                // increment the count if any digit
                // is equal to 1
                count++;
        }
  
        // Printing binary of decimal number
        System.out.print("The binary equivalent of " + num
                         + " is : ");
  
        // Iterating over array
        for (int j = i - 1; j >= 0; j--)
  
            // Printing obtained array in reverse order
            System.out.print(binary[j]);
  
        // Printing number of 1's
        System.out.println("\nNumber of 1s is : " + count);
    }
  
    // Main driver method
    public static void main(String[] args)
    {
        // Creating class GFG object in main
        GFG obj = new GFG();
  
        obj.convertAndCount(18);
        // calling convertAndCount() method on decimal
        // over the value 18
    }
}

输出

The binary equivalent of 18 is : 01001
Number of 1s is : 2