Java BitSet previousClearBit()用法及代码示例

BitSet是java.util包中定义的类。它创建一个由布尔值表示的位数组。

Bitset.previousClearBit()
此方法用于查找在作为参数传递的索引上或索引之前发生的错误位。此方法返回在指定的起始索引上或之前出现的，设置为false的最近位的索引。如果不存在这样的位，或者给定-1作为起始索引，则返回-1。

用法:

public int previousClearBit(int fromIndex)

参数：此方法采用fromIndex，它是要从其开始检查的索引(包括)。

返回值：此方法返回前一个清除位的索引，如果没有该位，则返回-1

异常：如果指定的索引小于-1，则此方法将引发IndexOutOfBoundsException。

以下示例程序旨在说明previousCleatBit()方法：

示例1:

// Java program illustrating Bitset 
// previousClearBit() function 
  
import java.util.*; 
public class GFG 
{ 
    public static void main(String[] args) 
    { 
        // Constructors of BitSet class 
        BitSet bs1 = new BitSet(); 
        BitSet bs2 = new BitSet(); 
        BitSet bs3 = new BitSet(); 
          
        /* assigning values to set1*/
        bs1.set(0); 
        //bs1.set(1); 
        bs1.set(2); 
        bs1.set(4); 
  
        // assign values to bs2 
        bs2.set(4); 
        bs2.set(6); 
        bs2.set(5); 
        bs2.set(1); 
        bs2.set(2); 
        bs2.set(3); 
        bs2.set(12); 
  
        // Printing the 2 Bitsets 
        System.out.println("bs1 : " + bs1); 
        System.out.println("bs2 : " + bs2); 
        System.out.println("bs3 : " + bs3); 
          
        // Performing previousClearBit() on bitsets 
        System.out.println("Previous Clear Bit of bs1"
+ bs1.previousClearBit(0)); 
        System.out.println("Previous Clear Bit of bs2"
+ bs2.previousClearBit(5)); 
        System.out.println("Previous Clear Bit of bs3"
+ bs3.previousClearBit(3)); 
          
    } 
}

输出：

bs1 : {0, 2, 4}
bs2 : {1, 2, 3, 4, 5, 6, 12}
bs3 : {}
Previous Clear Bit of bs1-1
Previous Clear Bit of bs20
Previous Clear Bit of bs33

示例2:要显示IndexOutOfBoundException：

// Java program illustrating Bitset 
// previousClearBit() function. 
  
import java.util.*; 
public class GFG { 
    public static void main(String[] args) 
    { 
        // Constructors of BitSet class 
        BitSet bs1 = new BitSet(); 
  
        // assigning values to set1 
        bs1.set(0); 
        bs1.set(1); 
        bs1.set(2); 
        bs1.set(4); 
  
        // Printing the Bitset 
        System.out.println("bs1 : " + bs1); 
  
        try { 
            // Passing -2 as parameter 
            System.out.println(bs1.previousClearBit(-2)); 
        } 
        catch (Exception e) { 
            System.out.println("Exception when "
                               + "index less than -1 is passed "
                               + "as parameter : " + e); 
        } 
    } 
}

输出：

bs1 : {0, 1, 2, 4}
Exception when index less than -1 is passed as parameter : java.lang.IndexOutOfBoundsException: fromIndex

相关用法

注：本文由纯净天空筛选整理自barykrg大神的英文原创作品 BitSet previousClearBit() method in Java。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。