10java基本课程—常用工具类.pptVIP

* * * * * 使用包装类Character的例子： class Test { public static void main(String[] args) { String str = 31; int a = Integer.parseInt(str, 17); System.out.println(a= + a); int letterCount = 0; int digitCount = 0; str = args[0]; for(int i = 0; i str.length(); i++) { char ch = str.charAt(i); if(Character.isLetter(ch)) { letterCount++; } else if(Character.isDigit(ch)) { digitCount++; } } System.out.println(字符串+ str + 含有 + letterCount + 个字母， + digitCount + 个数字。); } } * * * sort使用的完整例子： import java.util.*; class Test2 { static void t1() { int[] ary = {2, 7, 1, 4, 5, 9, 6}; System.out.println(Arrays.toString(ary)); Arrays.sort(ary); System.out.println(排序后： + Arrays.toString(ary)); Integer[] ary2 = {2, 7, 1, 4, 5, 9, 6}; System.out.println(排序前ary2:+ Arrays.toString(ary2)); Arrays.sort(ary2, new MyComparator()); System.out.println(排序后ary2:+ Arrays.toString(ary2)); } public static void main(String[] args) { Human[] hus = new Human[3]; hus[0] = new Human(Jack, 20); hus[1] = new Human(Tom, 30); hus[2] = new Human(Hans, 15); System.out.println(排序前: + Arrays.toString(hus)); Arrays.sort(hus, new HumanComp(Human.SORT_BY_NAME)); System.out.println(按名字排序后: + Arrays.toString(hus)); Arrays.sort(hus, new HumanComp(Human.SORT_BY_AGE)); System.out.println(按年龄排序后: + Arrays.toString(hus)); } } //对整数按降序排 class MyComparator implements Comparator { public int compare(Object o1, Object o2) { Integer t1 = (Integer)o1; Integer t2 = (Integer)o2; return t2 - t1; } } class Human { public static final int SORT_BY_NAME = 1; //升序 public static final int SORT_BY_AGE = 2; //降序 String name; int age; public Human(String name, int age) { = name; this.age = age; } public String toString() { return [ + name + , + age + ]; } } class HumanComp implements Comparator { int type = 0; //按什么比较 public HumanComp(int type) { this.type = type;