贴几个J2ME函数, 希望能对大家有用!

技术2022-05-11 25

swap( int a, int b) { a = a ^ b; b = a ^ b; a = a ^ b; }

/** * 求平方根 * @param value 定义域 * @return 值域 */ final public static int sqrt( int value) { int sqrt = 0; for (int k = 0x100000; k != 0; k >>= 2) { int tmp = sqrt + k; sqrt >>= 1; if (tmp <= value) { value -= tmp; sqrt += k; } } return sqrt; }

原理：先按行缩放，再按列缩放测试结果，在50MS以下 package com.gts.Util; import javax.microedition.lcdui. * ; public class GImageUtil { /** * 本次缩放操作的所用时间 * 以毫秒的形式 */ public static long timecost = 0; /** * 快速缩放一个图片 * 得到一个不带透明色的缩放後的图片 * 一般耗时在 50ms 以下 * @param imgSrc - 原始图片 * @param scale100 - 缩放比率，以百分比的形式，比如输入200，表示放大到原始的200%；输入75，表示缩小到原始的 75% * @return */ public static final Image fastScale(Image imgSrc, int scale100) { int width = imgSrc.getWidth(); int height = imgSrc.getHeight(); width *= scale100; width /= 100; height *= scale100; height /= 100; // return scale(imgSrc, width, height); return fastScale(imgSrc, width, height); } /** * 快速缩放 * @param imgSrc - 原始图片 * @param w_new - 新宽度 * @param h_new - 新高度 * @return - 缩放后的图片 */ public static final Image fastScale(Image src, int dstW ,int dstH) { long time = System.currentTimeMillis(); int srcW = src.getWidth(); int srcH = src.getHeight(); Image tmp = Image.createImage(dstW, srcH); Graphics g = tmp.getGraphics(); int delta = (srcW << 16) / dstW; int pos = delta >> 1; for (int x = 0; x < dstW; x++) { g.setClip(x, 0, 1, srcH); g.drawImage(src, x - (pos >> 16), 0, Graphics.LEFT | Graphics.TOP); pos += delta; } Image dst = Image.createImage(dstW, dstH); g = dst.getGraphics(); delta = (srcH << 16) / dstH; pos = delta >> 1; for (int y = 0; y < dstH; y++) { g.setClip(0, y, dstW, 1); g.drawImage(tmp, 0, y - (pos >> 16), Graphics.LEFT | Graphics.TOP); pos += delta; } // return dst; tmp = null; timecost = System.currentTimeMillis() - time; return dst; }

/**轮询次数计数器*/ static int sort_counter = 0 ; /**交换次数计数器*/ static int swap_counter = 0 ; /** * 冒泡排序法 * 从小到大 * @param data - 原始数据 * @param smallToBig - true if 从小到大; false if 从大到小 */ public static final void bubbleSort( int [] data, boolean smallToBig) { int high = data.length; int sort_start = sort_counter; int swap_start = swap_counter; for(int i = 0; i < high; i++) { for(int j = i; j < high; j++) { ++sort_counter; if(smallToBig) { if(data[i] > data[j]) { swapData(data, i, j); } } else { if(data[i] < data[j]) { swapData(data, i, j); } } } } Util.debug("bubbleSort::Sort_Counter::" + (sort_counter - sort_start) + "::swap_counter::" + (swap_counter - swap_start)); } /** * Quick sort 来排序一个数组 * 从小到大 * @param data - 要排序的数组 * @param smallToBig - true if 从小到大; false if 从大到小 */ public static final void quickSort( int [] data, boolean smallToBig) { int low = 0; int high = data.length - 1; int sort_start = sort_counter; int swap_start = swap_counter; quickSort(data, low, high, smallToBig); Util.debug("quickSort::Sort_Counter::" + (sort_counter - sort_start) + "::swap_counter::" + (swap_counter - swap_start)); } /** * 快速排序 * @param data - 原始数组 * @param low - * @param high */ private static final void quickSort( int [] data, int low, int high, boolean smallToBig) { if(low < high) { int pivot = partition(data, low, high, smallToBig); quickSort(data, low, pivot - 1, smallToBig); quickSort(data, pivot + 1, high, smallToBig); } } /** * 分割点 * @param data * @param low * @param high * @return */ private static final int partition( int [] data, int low, int high, boolean smallToBig) { //当前位置为第一个元素所在位置 int pos = low; //采用第一个元素位轴 int pivot = data[pos]; for(int i = low + 1; i <= high; i++) { ++sort_counter; if(smallToBig) { //从小到大 if(data[i] < pivot) { ++pos; swapData(data, pos, i); } } else { //从大到小 if(data[i] > pivot) { ++pos; swapData(data, pos, i); } } } swapData(data, low, pos); return pos; } /** * 交换数据 * @param data - 原始数组 * @param i * @param j */ private static final void swapData( int [] data, int i, int j) { int tmp = data[i]; data[i] = data[j]; data[j] = tmp; ++swap_counter; }

/** * Build a 8-byte array from a long. No check is performed on the * array length. * * @param n The number to convert. * @param b The array to fill. * @return A byte[]. */ public static byte [] toBytes( long n, byte [] b) { b[7] = (byte) (n); n >>>= 8; b[6] = (byte) (n); n >>>= 8; b[5] = (byte) (n); n >>>= 8; b[4] = (byte) (n); n >>>= 8; b[3] = (byte) (n); n >>>= 8; b[2] = (byte) (n); n >>>= 8; b[1] = (byte) (n); n >>>= 8; b[0] = (byte) (n); return b; } /** * Build a long from first 8 bytes of the array. * * @param b The byte[] to convert. * @return A long. */ public static long toLong( byte [] b) { return ((((long) b[7]) & 0xFF) + ((((long) b[6]) & 0xFF) << 8) + ((((long) b[5]) & 0xFF) << 16) + ((((long) b[4]) & 0xFF) << 24) + ((((long) b[3]) & 0xFF) << 32) + ((((long) b[2]) & 0xFF) << 40) + ((((long) b[1]) & 0xFF) << 48) + ((((long) b[0]) & 0xFF) << 56)); }

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