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今天就跟大家聊聊有关Android中任实现将 List中的对象以字段排序,可能很多人都不太了解,为了让大家更加了解,小编给大家总结了以下内容,希望大家根据这篇文章可以有所收获。
在Android开发中,有时我们需要对一个对象的集合按照某一个字段进行排序,
Bean
public class Student { private int studentId; private String studentName; private int age; public Student(int studentId , String studentName, int age){ this.studentId=studentId; this.studentName=studentName; this.age=age; } public int getStudentId() { return studentId; } public void setStudentId(int studentId) { this.studentId = studentId; } public String getStudentName() { return studentName; } public void setStudentName(String studentName) { this.studentName = studentName; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } }
实现排序
实现排序比较类 Comparator ,里面实现排序规则。
public class test { /** * @param args */ public static void main(String[] args) { Student stu1 = new Student (1,"zhangsan",28); Student stu2 = new Student (2,"zhagnsan",19); Student stu3 = new Student (3,"wangwu",19); Student stu4 = new Student (4,"wangwu",19); Student stu5 = new Student (5,"zhaoliu",18); ArrayList<Student> list = new ArrayList<Student>(); list.add(stu1); list.add(stu2); list.add(stu3); list.add(stu4); list.add(stu5); //排序规则,这里是以年龄先排序,如果年龄相同 Comparator<Student> comparator = new Comparator<Student>() { public int compare(Student s1, Student s2) { // 先排年龄 if (s1.getAge() != s2.getAge()) { return s1.getAge() - s2.getAge(); } else if (!s1.getStudentName().equals(s2.getStudentName())) { // 年龄相同则按姓名排序 return s1.getStudentName().compareTo(s2.getStudentName()); } else { // 姓名也相同则按学号排序 return s1.getStudentId() - s2.getStudentId(); } } }; //这里就会自动根据规则进行排序 Collections.sort(list,comparator); for(int i=0;i<list.size();i++){ Student stu=list.get(i); System.out.println("年龄:"+stu.getAge()+" 姓名:"+stu.getStudentName()+" 学号:"+stu.getStudentId()); } } }
排序结果
结果:
年龄:18 姓名:zhaoliu 学号:5
年龄:19 姓名:wangwu 学号:3
年龄:19 姓名:wangwu 学号:4
年龄:19 姓名:zhagnsan 学号:2
年龄:28 姓名:zhangsan 学号:1
也可以想下面这样写:
Collections.sort(list, new Comparator<GoodsBean>() { @Override public int compare(GoodsBean bean1, GoodsBean bean2) { if (Integer.valueOf(bean1.getScore()).compareTo(Integer.valueOf(bean2.getScore())) == 0) { return Integer.valueOf(bean1.getRecommend_num()).compareTo(Integer.valueOf(bean2.getRecommend_num())); } else { return Integer.valueOf(bean1.getScore()).compareTo(Integer.valueOf(bean2.getScore())); } } });
这样就可以对一个集合中的数据各种排序了。
补充知识:java利用映射表名称反射创建实体类并赋属性值
1.hibernate中首先进行初始化,将对应的表名和类名以键值对的方式存放到map中
private Map<String, String> mappings;//全局变量 /** * 根据数据库表名获取实体类 */ public void initMappings() { if (mappings == null) { mappings = new HashMap<String, String>(); SessionFactory factory = this.getSessionFactory(); Map metaMap = factory.getAllClassMetadata(); for (String key : (Set<String>) metaMap.keySet()) { AbstractEntityPersister classMetadata = (AbstractEntityPersister) metaMap.get(key); String tableName = classMetadata.getTableName().toLowerCase(); int index = tableName.indexOf("."); if (index >= 0) { tableName = tableName.substring(index + 1); } String className = classMetadata.getEntityMetamodel().getName(); mappings.put(tableName, className); } } }
2.调用方法,传入表名得到对应的实体类名
public String getEntityNameByTableName(String tableName) { initMappings(); return mappings.get(tableName); }
3.根据实体类名创建实体类
/** *listobj:要赋的属性值集合,顺序要和实体类属性顺序一致 */ public Object getByReflect(String tableName, List listobj)throws Exception { Class<?> model = Class.forName(tableName); Object object = new Object(); if (model != null) { Field[] field = model.getDeclaredFields(); String[] modelName = new String[field.length]; String[] modelType = new String[field.length]; object = model.newInstance(); Method m = null; for (int i = 1; i <field.length ; i++) { String name = field[i].getName(); Object value = null; name = name.substring(0, 1).toUpperCase() + name.substring(1); String type = field[i].getGenericType().toString(); if (type.equals("class java.lang.String")) { m = model.getDeclaredMethod("set" + name, String.class); if(listobj.get(i - 1) instanceof Double){ Double d=(Double) listobj.get(i-1); value=String.valueOf(d); }else{ value =(String)listobj.get(i - 1); } } if (type.equals("class java.lang.Integer")) { m = model.getDeclaredMethod("set" + name, Integer.class); Double d = (Double) listobj.get(i - 1); value = Integer.valueOf(d.intValue()); } if (type.equals("class java.lang.Short")) { m = model.getDeclaredMethod("set" + name, Short.class); value = (Short) listobj.get(i - 1); } if (type.equals("class java.lang.Float")) { m = model.getDeclaredMethod("set" + name, Float.class); value = (Float) listobj.get(i - 1); } if (type.equals("class java.lang.Double")) { m = model.getDeclaredMethod("set" + name, Double.class); value = (Double) listobj.get(i - 1); } if (type.equals("class java.lang.Boolean")) { m = model.getDeclaredMethod("set" + name, Boolean.class); value = (Boolean) listobj.get(i - 1); } if (m != null) { m.invoke(object, value); } } } return object; }
看完上述内容,你们对Android中任实现将 List中的对象以字段排序有进一步的了解吗?如果还想了解更多知识或者相关内容,请关注亿速云行业资讯频道,感谢大家的支持。
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