compare 应用实例

整理2个compare 接口排序的实现方法：

 

 

一、 自己实现比较方法，包括一些复杂的多条件比较

 

public class Comparator {
    private String mothdName;

    /**
     * 比较器，可以根据具体VO定制排序
     * @param mothdName
     * @return
     */
    public java.util.Comparator getComparator(final String mothdName) {
        this.mothdName = mothdName;
        return new java.util.Comparator() {
            public int compare(Object o1, Object o2) {
                if (o1 instanceof String) {
                    return compare((String) o1, (String) o2);
                } else if (o1 instanceof Integer) {
                    return compare((Integer) o1, (Integer) o2);
                }else if (o1 instanceof Timestamp) {
                    return compare((Integer) o1, (Integer) o2);
                }else if (o1 instanceof Date) {
                    return compare((Integer) o1, (Integer) o2);
                } else if (o1 instanceof BpmTaskVo) {
                    return compare((BpmTaskVo) o1, (BpmTaskVo) o2);
                } else {
                    System.err.println("未找到合适的比较器");
                    return 1;

                }
            }

            public int compare(String o1, String o2) {
                return o1.compareTo(o2);
            }
            public int compare(Integer o1, Integer o2) {
                return o1.compareTo(o2);
            }
            public int compare(Boolean o1, Boolean o2) {
                return o1.compareTo(o2);
            }
            public int compare(Timestamp o1, Timestamp o2){
                return o1.compareTo(o2);
            }
            public int compare(Date o1, Date o2){
                return o1.compareTo(o2);
            }


            //为BpmTaskVo 定制排序
            public int compare(BpmTaskVo vo1, BpmTaskVo vo2) {
                Class<BpmTaskVo> voClass = BpmTaskVo.class;
                Method mothdGet;
                // mGet.setAccessible(true);//因为写成private 取值可以不设置
                int i = 0;
                try {
                    mothdGet = voClass.getDeclaredMethod(mothdName);
                    Object o1 = mothdGet.invoke(vo1);
                    Object o2 = mothdGet.invoke(vo2);
//                  System.out.println("方法名"+mothdName + "比较值o1 = "+o1 + "    o2 = "+o2);
                    i = compare(o1,o2);
                } catch (Exception e) {
                    e.printStackTrace();
                }
                return i;
            }

            // 多条件比较
            public int compare(BpmTaskVo o1, BpmTaskVo o2) {
                String firstname1 = o1.getFirstName();
                String firstname2 = o2.getFirstName();
                String lastname1 = o1.getLastName();
                String lastname2 = o2.getLastName();
                Boolean sex1 = o1.getSex();
                Boolean sex2 = o2.getSex();
                Integer age1 = o1.getAge();
                Integer age2 = o2.getAge();
                return (compare(firstname1, firstname2) == 0 ? (compare(lastname1, lastname2) == 0 ? (compare(sex1, sex2) == 0 ? (compare(age1, age2) == 0 ? 0 : compare(age1, age2)) : compare(sex1, sex2)) : compare(lastname1, lastname2)) : compare(firstname1, firstname2));
            }
        };
    }

}

 

 

二、 利用反射和compareTo，动态比较。这种是比较好的方法

 

public class RmComparator {

    /**
     * 比较器，可以根据VO具体字段比较
     *
     * @param mothdName
     * @return
     */
    public Comparator getComparator(final String mothdName) {
        return new Comparator() {
            public int compare(Object o1, Object o2) {
                int val = 0;//默认不排序
                try {
                    if (mothdName == null) {
                        val = myCompare(o1, o2);
                    } else {
                        val = myCompare(getValue(o1, mothdName), getValue(o2, mothdName));
                    }
                } catch (Exception ex) {
                    ex.printStackTrace();
                }
                return val;
            }
            // VO中取值
            public Object getValue(Object bean, String methodName) throws Exception {
                Method getMethod = bean.getClass().getMethod(methodName, null);
                return getMethod.invoke(bean, null);
            }

            // 具体执行比较的方法
            public int myCompare(Object obj1, Object obj2) throws Exception {
                if (obj1 == null || obj2 == null){
                    return obj1 == null ? -1 : 1;
                }
                Class cl = obj1.getClass();
                if (obj1 instanceof java.lang.Comparable) {
                    // byte int long float..number, date , boolean , char,String
                    Method getMethod = obj1.getClass().getMethod("compareTo", new Class[] { cl });
                    return (Integer) getMethod.invoke(obj1, new Object[] { obj2 });
                }
                return 0;//默认不排序
            }
        };
    }