Compare string, sort, and compare string sorting

Compare string, sort, and compare string sorting
List <Map <String, Object> queryData = configDao. queryConfig (expressions, conditions, expressions); Collections. sort (queryData, new Comparator <Map <String, Object> () {public int compare (Map <String, Object> o1, Map <String, Object> o2) {// Integer name1 = Integer. valueOf (o1.get ("category "). toString (); // name1 is an Integer obtained from your list. // Integer name2 = Integer. valueOf (o2.get ("category "). toString (); // name1 is the second name from your list // return name1.compareTo (name2); return o1.get ("category "). toString (). compareTo (o2.get ("category "). toString () ;}}); Comparator built-in function. queryDate is the list array to be sorted, followed by the sorting rule,Compare (a, B) method: return a negative integer, zero, or positive integer based on the first parameter smaller than, equal to, or greater than the second parameter.
Equals (obj) method: returns true only when the specified object is also a Comparator and forcibly implements the same sorting as this Comparator. The second parameter of Collections. sort (list, new PriceComparator (); returns an int value, which is equivalent to a flag, telling the sort method in what order to sort the list. Example: Package com. tjcyjd. comparator; import java. util. arrayList; import java. util. collections; import java. util. comparator; import java. util. gregorianCalendar; import java. util. iterator; import java. util. list; public class UseComparator {public static void main (String args []) {List <Book> list = new ArrayList <Book> (); // array sequence Book b1 = new Book (10000, "Dream of Red Mansions", 150.86, new GregorianCalendar (2009, 01, 25), "Cao Xueqin, Gao e "); book b2 = new Book (10001, "Romance of the Three Kingdoms", 99.68, new GregorianCalendar (2008, 7, 8), "Luo Guanzhong"); Book b3 = new Book (10002, "Water Margin", 100.8, new GregorianCalendar (2009, 6, 28), "Shi Nai"); Book b4 = new Book (10003, "Journey to the West", 120.8, new GregorianCalendar (2011, 6, 8), "Wu chengen"); Book b5 = new Book (10004, "tianlong Babu", 10.4, new GregorianCalendar (2011, 9, 23), "Sohu "); list. add (b1); list. add (b2); list. add (b3); list. add (b4); list. add (b5); // Collections. sort (list); // No Default comparator, cannot sort System. out. println ("elements in the array sequence:"); myprint (list); Collections. sort (list, new PriceComparator (); // sort System by price. out. println ("sort by book price:"); myprint (list); Collections. sort (list, new CalendarComparator (); // sort System by time. out. println ("sort by Book Publishing Time:"); myprint (list) ;}// custom comparator: sort by Book price static class PriceComparator implements Comparator {public int compare (Object object1, Object object2) {// method Book p1 = (Book) object1 in the implementation interface; // forcibly convert Book p2 = (Book) object2; return new Double (p1.price ). compareTo (new Double (p2.price) ;}// custom Comparator: sort by book publication time static class CalendarComparator implements Comparator {public int compare (Object object1, Object object2) {// method Book p1 = (Book) object1 in the implementation interface; // forcibly convert Book p2 = (Book) object2; return p2.calendar. compareTo (p1.calendar) ;}// custom method: The Branch prints out the public static void myprint (list <Book> List) {Iterator it = list. iterator (); // get iterator, used to traverse all elements in the list while (it. hasNext () {// returns true System if the iterator contains elements. out. println ("\ t" + it. next (); // display this element}
}} RewriteThe compare method can also add columns