Java.util.BitSet 类方法在 Java 中用示例| Set 2

原文:https://www . geesforgeks . org/bitset-class-methods-Java-examples-set-2/

Methods discussed in this post:
                       BitSet class methods.
               /      /     |      |       \       \
           set()  xor()  clone() clear()  length()  cardinality()

我们强烈建议将以下第 1 组作为先决条件。 Java 中的 BitSet 类| Set 1

  1. set():Java . util . bitset . set()方法是将指定索引处的位设置为指定值。 语法:

    ```java public void set(int bitpos) public void set(int bitpos, boolean val) Parameters: bitpos : a bit index val : a boolean value to set Return: Nothing Throws: IndexOutOfBoundsException - if the specified index is negative

    ```

  2. clone():Java . util . BitSet . clone()方法克隆一个 BitSet，产生一个与其相等的新 BitSet。该位集的克隆是另一个位集，它具有与该位集完全相同的设为真的位。 语法:

    ```java public Object clone() Return: a clone of this bit set

    ```

  3. 基数:Java . util . BitSet . cardinality()方法用于查找 Bitset 中的元素个数。 语法:

public int cardinality()
Return: the number of bits set to true in this BitSet.

// Java program explaining BitSet class methods
// set(), clone(), cardinality()
import java.util.*;
public class NewClasss
{
    public static void main(String[] args)
    {
        BitSet bs1 = new BitSet();
        BitSet bs2 = new BitSet(8);
        BitSet bs3 = new BitSet();

        // assign values to bs1 using set()
        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);

        // Here we are using .clone() method to make
        // bs3 as bs1
        bs3 = (BitSet) bs1.clone();

        // Printing the 3 Bitsets
        System.out.println("bs1 : " + bs1);
        System.out.println("bs2 : " + bs2);
        System.out.println("bs3 cloned from bs1 : " + bs3);

        // Using .cardinality() method to print the no. of
        // elements of Bitset
        System.out.println("Cardinality of bs1 : " +
                                       bs1.cardinality());
        System.out.println("Cardinality of bs2 : " +
                                       bs2.cardinality());
    }
}

输出:

bs1 : {0, 1, 2, 4}
bs2 : {4, 5, 6}
bs3 cloned from bs1 : {0, 1, 2, 4}
Cardinality of bs1 : 4
Cardinality of bs2 : 3

  • clear():Java . util . BitSet . clear()方法用于清除元素，即将所有 Bitset 元素设置为 false。 语法:

    ```java public void clear(int frompos,int topos) public void clear(int bitIndex) public void clear() Parameters: frompos - index of the first bit to be cleared topos - index after the last bit to be cleared bitIndex - the index of the bit to be cleared Throws: IndexOutOfBoundsException - if pos value is negative or frompos is larger than topos

    ```

    • xor() : java.util.BitSet.xor() method performs the logical Xor operation on the bitsets. This bit set is modified so that a bit in it has the value true if and only if :
    • 该位最初的值为 true，参数中对应的位的值为 false。
    • 该位最初的值为 false，参数中对应的位的值为 true。

    语法:

    ```java public void xor(BitSet set) Parameters: set - the BitSet with which we need to perform operation

    ```

    • length() : java.util.BitSet.length() method return returns logical size of the bitset. The index of the highest set bit in the bitset plus one. Returns zero if the bitset contains no set bits. Syntax:

    ```java public int length() Returns: the logical size of this BitSet

    ```

    ```java // Java program explaining BitSet class methods //  xor(), length(), clear() methods import java.util.*; public class NewClass {     public static void main(String[] args)     {         BitSet bs1 = new BitSet();         BitSet bs2 = new BitSet();

    // assign values to bs1 using set()         bs1.set(7);         bs1.set(1);         bs1.set(2);         bs1.set(4);         bs1.set(3);         bs1.set(6);

    // assign values to bs2         bs2.set(4);         bs2.set(6);         bs2.set(3);         bs2.set(9);         bs2.set(2);

    // Printing the Bitsets         System.out.println("bs1 : " + bs1);         System.out.println("bs2 : " + bs2);

    // use of length() method         System.out.println("use of length() : " + bs1.length());

    // use of xor() to perform logical Xor operation         bs1.xor(bs2);         System.out.println("Use of xor() : " + bs1);         bs2.xor(bs1);         System.out.println("Use of xor() : " + bs2);

    // clear from index 2 to index 4 in bs1         bs2.clear(1, 2);         System.out.println("bs2 after clear method : " + bs2);

    // clear complete Bitset         bs1.clear();         System.out.println("bs1 after clear method : " + bs1);     } } ```

    输出:

    ```java bs1 : {1, 2, 3, 4, 6, 7} bs2 : {2, 3, 4, 6, 9} use of length() : 8 Use of xor() : {1, 7, 9} Use of xor() : {1, 2, 3, 4, 6, 7} bs2 after clear method : {2, 3, 4, 6, 7} bs1 after clear method : {}

    ```

    Java 中的 BitSet 类方法示例| Set 3

    参考文献: https://docs . Oracle . com/javase/7/docs/API/Java/util/bitset . html

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