Java Integer.estimOneBit()方法

java.lang的Integer.estimOneBit()方法返回一个整数值，该整数值最多只有一个位，位于给定int值的最高阶（即最左边）的一个位的位置。如果指定的值在其二进制补码表示中没有一比特，那么它将返回0，如果它等于0，则简单地返回。

语法

public static int highestOneBit( _int a_ )

参数： 该方法需要一个整数类型的参数 a ，指的是要返回的最高阶位的值或要对其进行的操作。

返回： 该方法可以返回两种类型的值。

• 返回一个带有单个1位的整数值，位于指定值中最高阶1位的位置。
• 如果指定的值等于零，则返回零。

例子

Input: 19
Output: Highest one bit of the given integer is = 16

Input: -9
Output: Highest one bit of the given integer is = -2147483648

**Explanation:**
Consider any integer a = 19
Binary Representation = 0001 0011
Highest bit(at 4) i.e.0001 0000
so result = 2^4=16

下面的程序说明了Java.lang.Integer.highestOneBit()方法。
程序1： 对于一个正数。

// Java program to illustrate the
// Java.lang.Integer.highestOneBit() Method
import java.lang.*;
 
public class HighestOneBit {
 
    public static void main(String[] args)
    {
 
        int a = 29;
        System.out.println("Number is = " + a);
 
        // returns an int value with at most a single one-bit, in the position
        // of the highest-order or the leftmost one-bit in the specified int value
        System.out.print("Highest one bit of the given integer is = ");
        System.out.println(Integer.highestOneBit(a));
        a = 44;
        System.out.println("Number is = " + a);
        System.out.print("Highest one bit of the given integer is = ");
        System.out.println(Integer.highestOneBit(a));
    }
}

输出

Number is = 29
Highest one bit of the given integer is = 16
Number is = 44
Highest one bit of the given integer is = 32

程序2： 对于一个负数。

// Java program to illustrate the
// Java.lang.Integer.highestOneBit() Method
import java.lang.*;
 
public class HighestOneBit {
 
    public static void main(String[] args)
    {
 
        int a = -9;
        System.out.println("Number is = " + a);
 
        // returns an int value with at most a single one-bit, in the position
        // of the highest-order or the leftmost one-bit in the specified int value
        System.out.print("Highest one bit of the given integer is = ");
        System.out.println(Integer.highestOneBit(a));
    }
}

输出

Number is = -9
Highest one bit of the given integer is = -2147483648

程序3： 对于一个十进制数值。
注意： 由于类型不兼容，当十进制数值作为一个参数被传递时，它将返回一个错误信息。

// Java program to illustrate the
// Java.lang.Integer.highestOneBit() Method
import java.lang.*;
 
public class HighestOneBit {
 
    public static void main(String[] args)
    {
 
        int a = 84.22;
        System.out.println("Number is = " + a);
 
        // decimal value 84.22 is passed here
        System.out.print("Highest one bit of the given integer is = ");
        System.out.println(Integer.highestOneBit(a));
    }
}

输出

prog.java:9: error: incompatible types: possible lossy conversion from double to int
    int a = 84.22;
            ^
1 error

程序4： 对于一个字符串。
注意： 当一个字符串作为参数被传递时，由于类型不兼容，它将返回一个错误信息。

// Java program to illustrate the
// Java.lang.Integer.highestOneBit() Method
import java.lang.*;
 
public class HighestOneBit {
 
    public static void main(String[] args)
    {
 
        int a = "34";
        System.out.println("Number is = " + a);
 
        // decimal value 84.22 is passed here
        System.out.print("Highest one bit of the given integer is = ");
        System.out.println(Integer.highestOneBit(a));
    }
}

输出

prog.java:9: error: incompatible types: String cannot be converted to int
    int a = "34";
            ^
1 error