list的排序Comparator的compare(T lhs, T rhs)

归纳总结

public int compare(T lhs, T rhs)
返回值有1,0,-1
1. 升序排列，如何通过返回值控制？
当lhs.property>rhs.property返回1；lhs.property==rhs.property返回0；lhs.property<rhs.property返回-1。
2. 降序排列，如何通过返回值控制？
当lhs.property>rhs.property返回-1；lhs.property==rhs.property返回0；lhs.property<rhs.property返回1。
3. 组合排列，如何通过返回值控制？
以本测试代码为例，默认选中(defaultFlag==1)的地址第一个显示，剩下的按id升序排列
第一层判断defaultFlag
当lhs.defaultFlag==rhs.defaultFlag，进行第二层判断，判断id
注：lhs.property指一个字符的unicode值

测试代码

/** * @author :renpan * @version :v1.0 * @class :com.luomo.addressselected * @date :2016-08-15 11:41 * @description: */public class Test {    public static void main(String[] args) {        List<AddressDomain> addresses = new ArrayList<AddressDomain>();        addresses.add(new AddressDomain("1", "曹阿瞒", "18710990897", "0"));        addresses.add(new AddressDomain("2", "关羽", "18710990896", "0"));        addresses.add(new AddressDomain("3", "刘备", "18710990895", "0"));        addresses.add(new AddressDomain("4", "司马懿", "18710990894", "1"));        addresses.add(new AddressDomain("5", "张飞", "18710990893", "0"));        addresses.add(new AddressDomain("6", "诸葛亮", "18710990892", "0"));        Collections.sort(addresses, new Comparator<AddressDomain>() {            @Override            public int compare(AddressDomain lhs, AddressDomain rhs) {                //CODE_1:升序排列                /*if(Integer.parseInt(lhs.getId())>Integer.parseInt(rhs.getId())){                    return 1;                }else if(Integer.parseInt(lhs.getId())==Integer.parseInt(rhs.getId())){                    return 0;                }else{                    return -1;                }*/                //CODE_2:降序排列                /*if(Integer.parseInt(lhs.getId())>Integer.parseInt(rhs.getId())){                    return -1;                }else if(Integer.parseInt(lhs.getId())==Integer.parseInt(rhs.getId())){                    return 0;                }else{                    return 1;                }*/                //CODE_3:组合排列                if (Integer.parseInt(lhs.getDefaultFlag()) > Integer.parseInt(rhs.getDefaultFlag())) {                    return -1;                } else if (Integer.parseInt(lhs.getDefaultFlag()) == Integer.parseInt(rhs.getDefaultFlag())) {                    if (Integer.parseInt(lhs.getId()) > Integer.parseInt(rhs.getId())) {                        return 1;                    } else if (Integer.parseInt(lhs.getId()) == Integer.parseInt(rhs.getId())) {                        return 0;                    } else {                        return -1;                    }                } else {                    return 1;                }            }        });        for (int i = 0; i < addresses.size(); i++) {            System.out.println(addresses.get(i).toString());        }    }}

结果

CODE_1:升序排列 id

AddressDomain{id='1', name='曹阿瞒', mobilePhone='18710990897', defaultFlag='0'}AddressDomain{id='2', name='关羽', mobilePhone='18710990896', defaultFlag='0'}AddressDomain{id='3', name='刘备', mobilePhone='18710990895', defaultFlag='0'}AddressDomain{id='4', name='司马懿', mobilePhone='18710990894', defaultFlag='1'}AddressDomain{id='5', name='张飞', mobilePhone='18710990893', defaultFlag='0'}AddressDomain{id='6', name='诸葛亮', mobilePhone='18710990892', defaultFlag='0'}

CODE_2:降序排列 id

AddressDomain{id='6', name='诸葛亮', mobilePhone='18710990892', defaultFlag='0'}AddressDomain{id='5', name='张飞', mobilePhone='18710990893', defaultFlag='0'}AddressDomain{id='4', name='司马懿', mobilePhone='18710990894', defaultFlag='1'}AddressDomain{id='3', name='刘备', mobilePhone='18710990895', defaultFlag='0'}AddressDomain{id='2', name='关羽', mobilePhone='18710990896', defaultFlag='0'}AddressDomain{id='1', name='曹阿瞒', mobilePhone='18710990897', defaultFlag='0'}

CODE_3:组合排列 defaultFlag>id(如果要根据姓名排序，要先获取汉字的拼音，再比较)

AddressDomain{id='4', name='司马懿', mobilePhone='18710990894', defaultFlag='1'}AddressDomain{id='1', name='曹阿瞒', mobilePhone='18710990897', defaultFlag='0'}AddressDomain{id='2', name='关羽', mobilePhone='18710990896', defaultFlag='0'}AddressDomain{id='3', name='刘备', mobilePhone='18710990895', defaultFlag='0'}AddressDomain{id='5', name='张飞', mobilePhone='18710990893', defaultFlag='0'}AddressDomain{id='6', name='诸葛亮', mobilePhone='18710990892', defaultFlag='0'}

源码释义

    /**     * Compares the two specified objects to determine their relative ordering.      * 比较两个指定的对象以决定它们的相对顺序     * The ordering implied by the return value of this method for all possible pairs of     * {@code (lhs, rhs)} should form an <i>equivalence relation</i>.     * 这个顺序排列是依赖于compare函数的返回值     * This means that     * <ul>     * <li>{@code compare(a,a)} returns zero for all {@code a}</li>     * compare(a,a)返回0     * <li>the sign of {@code compare(a,b)} must be the opposite of the sign of {@code     * compare(b,a)} for all pairs of (a,b)</li>     * compare(a,b)与compare(b,a)返回值是相反的     * <li>From {@code compare(a,b) > 0} and {@code compare(b,c) > 0} it must     * follow {@code compare(a,c) > 0} for all possible combinations of {@code     * (a,b,c)}</li>     * </ul>     * compare(a,b) > 0、compare(b,c) > 0则compare(a,c) > 0     *     * @param lhs     *            an {@code Object}.     * @param rhs     *            a second {@code Object} to compare with {@code lhs}.     * @return an integer < 0 if {@code lhs} is less than {@code rhs}, 0 if they are     *         equal, and > 0 if {@code lhs} is greater than {@code rhs}.     * @throws ClassCastException     *                if objects are not of the correct type.     */    public int compare(T lhs, T rhs);