BitSetDemo2 进行数字排序

package Datess;


import java.util.Arrays;
import java.util.BitSet;


public class BitSetDemo2 {


/**
* 求一个字符串包含的char
* 
*/
public static void containChars(String str) {
BitSet used = new BitSet();
for (int i = 0; i < str.length(); i++)
used.set(str.charAt(i)); // set bit for char


StringBuilder sb = new StringBuilder();
sb.append("[");
int size = used.size();
System.out.println(size);
for (int i = 0; i < size; i++) {
if (used.get(i)) {
sb.append((char) i);
}
}
sb.append("]");
System.out.println(sb.toString());
}


/**
* 求素数 有无限个。一个大于1的自然数，如果除了1和它本身外，不能被其他自然数整除(除0以外）的数称之为素数(质数） 否则称为合数
*/
public static void computePrime() {
BitSet sieve = new BitSet(1024);
int size = sieve.size();
for (int i = 2; i < size; i++)
sieve.set(i);
int finalBit = (int) Math.sqrt(sieve.size());


for (int i = 2; i < finalBit; i++)
if (sieve.get(i))
for (int j = 2 * i; j < size; j += i)
sieve.clear(j);


int counter = 0;
for (int i = 1; i < size; i++) {
if (sieve.get(i)) {
System.out.printf("%5d", i);
if (++counter % 15 == 0)
System.out.println();
}
}
System.out.println();
}

/**
* 进行数字排序
*/
public static void sortArray() {
int[] array = new int[] { 423, 700, 9999, 2323, 356, 6400, 1,2,3,2,2,2,2 };
BitSet bitSet = new BitSet(2 << 13);
// 虽然可以自动扩容，但尽量在构造时指定估算大小,默认为64
System.out.println("BitSet size: " + bitSet.size());


for (int i = 0; i < array.length; i++) {
bitSet.set(array[i]);
}
//剔除重复数字后的元素个数
int bitLen=bitSet.cardinality();


//进行排序，即把bit为true的元素复制到另一个数组
int[] orderedArray = new int[bitLen];
int k = 0;
for (int i = bitSet.nextSetBit(0); i >= 0; i = bitSet.nextSetBit(i + 1)) {
orderedArray[k++] = i;
}


System.out.println("After ordering: ");
for (int i = 0; i < bitLen; i++) {
System.out.print(orderedArray[i] + "\t");
}

System.out.println("iterate over the true bits in a BitSet");
//或直接迭代BitSet中bit为true的元素iterate over the true bits in a BitSet
for (int i = bitSet.nextSetBit(0); i >= 0; i = bitSet.nextSetBit(i + 1)) {
System.out.print(i+"\t");
}
System.out.println("---------------------------");
}

/**
* 将BitSet对象转化为ByteArray
* @param bitSet
* @return
*/
public static byte[] bitSet2ByteArray(BitSet bitSet) {
        byte[] bytes = new byte[bitSet.size() / 8];
        for (int i = 0; i < bitSet.size(); i++) {
            int index = i / 8;
            int offset = 7 - i % 8;
            bytes[index] |= (bitSet.get(i) ? 1 : 0) << offset;
        }
        return bytes;
    }
 
/**
* 将ByteArray对象转化为BitSet
* @param bytes
* @return
*/
    public static BitSet byteArray2BitSet(byte[] bytes) {
        BitSet bitSet = new BitSet(bytes.length * 8);
        int index = 0;
        for (int i = 0; i < bytes.length; i++) {
            for (int j = 7; j >= 0; j--) {
                bitSet.set(index++, (bytes[i] & (1 << j)) >> j == 1 ? true
                        : false);
            }
        }
        return bitSet;
    }

/**
* 简单使用示例
*/
public static void simpleExample() {
String names[] = { "Java", "Source", "and", "Support" };
BitSet bits = new BitSet();
for (int i = 0, n = names.length; i < n; i++) {
if ((names[i].length() % 2) == 0) {
bits.set(i);
}
}


System.out.println(bits);
System.out.println("Size : " + bits.size());
System.out.println("Length: " + bits.length());
for (int i = 0, n = names.length; i < n; i++) {
if (!bits.get(i)) {
System.out.println(names[i] + " is odd");
}
}
BitSet bites = new BitSet();
bites.set(0);
bites.set(1);
bites.set(2);
bites.set(3);
bites.andNot(bits);
System.out.println(bites);
}


public static void main(String args[]) {
//BitSet使用示例
BitSetDemo2.containChars("How do you do? 你好呀");
BitSetDemo2.computePrime();
BitSetDemo2.sortArray();
BitSetDemo2.simpleExample();


//BitSet与Byte数组互转示例
BitSet bitSet = new BitSet();
        bitSet.set(3, true);
        bitSet.set(98, true);
        System.out.println(bitSet.size()+","+bitSet.cardinality());
        //将BitSet对象转成byte数组
        byte[] bytes = BitSetDemo2.bitSet2ByteArray(bitSet);
        System.out.println(Arrays.toString(bytes));
         
        //在将byte数组转回来
        bitSet = BitSetDemo2.byteArray2BitSet(bytes);
        System.out.println(bitSet.size()+","+bitSet.cardinality());
        System.out.println(bitSet.get(3));
        System.out.println(bitSet.get(98));
        for (int i = bitSet.nextSetBit(0); i >= 0; i = bitSet.nextSetBit(i + 1)) {
System.out.print(i+"\t");
}
}
}