分类 Android 下的文章

Java 工具类将一个类中的值通过setter和getter传递给另一个类型public static <T> T entityToDto(Object entity, Class<T> dtoType) { T instance; try { instance = dtoType.getDeclaredConstructor().newInstance(); } catch (InstantiationException | IllegalAccessException | InvocationTargetException | NoSuchMethodException e) { throw new RuntimeException(e); } // 反射entity 获取getter Class<?> entryType = entity.getClass(); Arrays.stream(dtoType.getMethods()).filter( method -> method.getName().startsWith("set") ).forEach(method -> { String methodName = method.getName().replace("set", "get"); try { Object value = entryType.getMethod(methodName).invoke(entity); method.invoke(instance, value); } catch (NoSuchMethodException | IllegalAccessException | InvocationTargetException ignore) {} }); return instance; }

2022年05月12日
105 阅读
0 评论
1 点赞

计算Map初始容量算法在实际开发中经常需要使用到Map，但给Map一个怎样的初始容量比较合理？众所周知是最接近(要大于)数据长度的2的N次方那么，如何计算？欢迎指出错误/** * 计算Map初始容量 * @author 枫铃也 * @since 2019-10-09 15:51 */ public class CapacityUtil { private static final double MODULE = 2; public static int getCapacityFactor(int size) { int n = size; int power = 0; while (n > 1) { power++; n >>>= 1; } int capacity = (int) Math.pow(MODULE, power); if (capacity < size || capacity % MODULE != 0) { capacity *= MODULE; } return capacity; } }欢迎指出错误

2019年10月11日
116 阅读
0 评论
1 点赞

2019-10-10

Java阿拉伯数字转中文数字带单位转换的我只将数字范围定在十万以内的正数并且没考虑 0需要向上调整范围的童鞋自己修改代码呦欢迎指出错误先看效果再看代码不多说屁话上代码/** * @description: 阿拉伯数字转中文数字(不带单位) * @method: numberConvertToBaseChinese * @author: 枫铃也 * @since: 2019-10-10 16:03 * * @return java.lang.String */ public static String numberConvertToBaseChinese(int num) { StringBuffer buffer = new StringBuffer(); char[] nums = {'零', '一', '二', '三', '四', '五', '六', '七', '八', '九'}; char[] baseChar = Integer.toString(num).toCharArray(); for (char c : baseChar) { buffer.append(nums[c - 48]); } return buffer.toString(); } /** * @description: 阿拉伯数字转中文数字(带单位) * @method: numberConvertToChinese * @author: 枫铃也 * @since: 2019-10-10 16:03 * * @return java.lang.String */ public static String numberConvertToChinese(int num) { char[] nums = {'零', '一', '二', '三', '四', '五', '六', '七', '八', '九'}; char[] units = {' ', '十', '百', '千', '万'}; char[] baseChar = Integer.toString(num).toCharArray(); char[] numChar = new char[baseChar.length]; for (int i = 0; i < baseChar.length; i++) { numChar[i] = nums[baseChar[i] - 48]; } char[] unit = new char[numChar.length]; unit = Arrays.copyOf(units, unit.length); StringBuffer buffer = new StringBuffer(); for (int i = 0; i < numChar.length; i++) { if (numChar[i] != nums[0]) { buffer.append(numChar[i]).append(unit[unit.length - i - 1]); }else { buffer.append(numChar[i]); } } int index = 0; while ((index = buffer.indexOf(nums[0] + String.valueOf(nums[0]))) > 0) { buffer.replace(index, index + 2, String.valueOf(nums[0])); } return buffer.toString().substring(0, buffer.length() - 1); }神马，没有注释？我故意的（此处拒绝板砖和拖鞋之类的具有任何杀伤性的物品），嘿嘿自己看懂了才算是有收获欢迎指出错误

2019年10月10日
49 阅读
0 评论
0 点赞

2019年10月09日
61 阅读
0 评论
0 点赞

Java 8 的一些集合操作将一个对象集合中的某一个字段取出来生成一个新的集合List<Store> storeList = storeService.listStore(page, size); List<Integer> collect = storeList.stream().map(s -> s.getStoreId()).collect(Collectors.toList()); //OR List<Integer> collect = storeList.stream().map(Store::getStoreId).collect(Collectors.toList());将List对象集合转化为key为对象ID的MapList<Specification> specifications = specificationService.listSpecification(); Map<Integer, Specification> collect = specifications.stream().collect(Collectors.toMap(Specification::getSpecificationId, Function.identity()));跟据某个属性分组Map<String, List<PersonData>> collect = list.stream().collect(Collectors.groupingBy(PersonData::getType));根据某个属性分组，汇总某个属性Map<String, Integer> collect2 = list.stream().collect(Collectors.groupingBy(PersonData::getType,Collectors.summingInt(PersonData::getAge)));根据某个属性添加条件过滤数据list = list.stream().filter(u -> !u.getType().equals("访客")).collect(Collectors.toList());判断一组对象里面有没有属性值是某个值boolean add = list.stream().anyMatch(m -> "王五".equals(m.getName()));

2019年10月02日
97 阅读
0 评论
0 点赞

2019-06-03

Android使用贝塞尔曲线画心形一开始我只是想画个圆，可画着画着就成了心形，那就将错就错1. 创建一个Activity RelativeLayout container = findViewById(R.id.download_container); DisplayMetrics metrics = new DisplayMetrics(); getWindowManager().getDefaultDisplay().getMetrics(metrics); deviceWidth = metrics.widthPixels; deviceHeight = metrics.heightPixels; Circle circle = new Circle(this, deviceWidth / 2, deviceHeight / 2, deviceWidth / 8); Line line = new Line(this, deviceWidth / 2, deviceHeight / 2, deviceWidth / 8); container.addView(line);2. 创建一个自定义的Viewimport android.content.Context; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.graphics.Path; import android.graphics.PointF; import android.view.View; public class Line extends View { private Paint mPaint; private PointF startPointF; private PointF endPointF; private PointF controlPointF1, controlPointF2; private PointF startPointF2; private PointF endPointF2; private PointF controlPointF3, controlPointF4; public Line(Context context, float x, float y, float radius) { super(context); double d = (2 * Math.sqrt(2) - 1); this.startPointF = new PointF(x, y - radius); this.endPointF = new PointF(x, y + radius / 10); this.controlPointF1 = new PointF(x, (float) (y - d * radius)); this.controlPointF2 = new PointF((float) (x + d * radius), (float) (y - d * radius)); this.startPointF2 = new PointF(x, y - radius); this.endPointF2 = new PointF(x, y + radius / 10); this.controlPointF3 = new PointF(x, (float) (y - d * radius)); this.controlPointF4 = new PointF((float) (x - d * radius), (float) (y - d * radius)); this.mPaint = new Paint(Paint.ANTI_ALIAS_FLAG); this.mPaint.setColor(Color.WHITE); } @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); //绘制贝塞尔曲线 Path path = new Path(); path.moveTo(startPointF.x, startPointF.y); path.cubicTo(controlPointF1.x, controlPointF1.y, controlPointF2.x, controlPointF2.y, endPointF.x, endPointF.y); canvas.drawPath(path, mPaint); path.moveTo(startPointF2.x, startPointF2.y); path.cubicTo(controlPointF3.x, controlPointF3.y, controlPointF4.x, controlPointF4.y, endPointF2.x, endPointF2.y); canvas.drawPath(path, mPaint); } }运行效果

2019年06月03日
151 阅读
0 评论
0 点赞

枫铃也

绿水本无忧，因风皱面

青山原不老，为雪白头