package studyjava; import javax.xml.parsers.SAXParser; import java.io.StringReader; import java.util.Arrays; import java.util.Scanner; public class Start2 { public void Ch() { // String ch1 = "asAG53GAFgASDfmladg164"; String ch1; Scanner x = new Scanner(System.in); ch1 = x.nextLine(); char[] cha = ch1.toCharArray(); //转换成数组 // 开始判断大小字符和数字 for (int i = 0; i < cha.length; i++) { if (cha[i] < '9' && cha[i] > '0' || cha[i] < 'a') { System.out.println(cha[i]); } } } public void RanC() { char[] ch = new char[5]; char start = '0'; char end = 'z' + 1; for (int i = 0; i < ch.length; i++) { while (true) { char s = (char) (Math.random() * (end - start) + start); if (Character.isLetter(s) || Character.isDigit(s)) { ch[i] = s; break; } } } for (char c : ch) { System.out.println(c); } } public String randomString(int k) { char[] sa = new char[k]; for (int i = 0; i < k; i++) { while (true) { char x = (char) (Math.random() * 'z' + 1); if (Character.isLetter(x) || Character.isDigit(x)) { sa[i] = x; break; } } } String s = new String(sa); return s; } public void RS() { //创建一个长度是8的字符串数组 //使用8个长度是5的随机字符串初始化这个数组 //对这个数组进行排序，按照每个字符串的首字母排序(无视大小写) // //注1： 不能使用Arrays.sort() 要自己写 //注2： 无视大小写，即 Axxxx 和 axxxxx 没有先后顺序 String[] Sa = new String[8]; for (int i = 0; i < Sa.length; i++) { Sa[i] = randomString(5); } for (int i = 0; i < Sa.length; i++) { for (int j = 0; j < Sa.length - 1 - i; j++) { if (Character.toLowerCase(Sa[j].charAt(0)) >= Character.toLowerCase(Sa[j + 1].charAt(0))) { String temp = Sa[j + 1]; Sa[j + 1] = Sa[j]; Sa[j] = temp; } } } for (String x : Sa) { System.out.println(x); } } /*1. 生成一个长度是3的随机字符串，把这个字符串作为当做密码 2. 使用穷举法生成长度是3个字符串，匹配上述生成的密码 要求： 分别使用多层for循环 和 递归解决上述问题 */ public void secret() { String st = randomString(3); System.out.println(st); char[] ss = st.toCharArray(); char[] guess = new char[3]; for (int i = 0; i < ss.length; i++) { for (char j = 0; j < 'z'; j++) { if (j == ss[i]) { guess[i] = j; } } } String m = new String(guess); System.out.println(m); } // // public char concern(){ // while(true){ // // } // } public void LetterC() { String n = " i am bAt man "; String t = n.trim(); String[] cc = t.split(" "); // for (String x:cc){System.out.println(x);} for (int i = 0; i < cc.length; i++) { String m = cc[i]; char z = Character.toUpperCase(m.charAt(0)); String a = m.substring(1); String nn = a.toLowerCase(); String b = z + nn; cc[i] = b; } for (String x : cc) { System.out.println(x); } } public void Rkl() { String rkl = "peter piper picked a peck of pickled peppers"; String[] duanc = rkl.split(" "); int num = 0; for (int i = 0; i < duanc.length; i++) { if (duanc[i].charAt(0) == 'p') { num++; } } System.out.println(num); } public void GU() { String w = "dsfadgjarjg"; char[] d = w.toCharArray(); for (int i = 0; i < d.length; i++) { if (i % 2 == 0) { d[i] = Character.toUpperCase(d[i]); } } String www = new String(d); System.out.println(www); } public void LW() { String ss = "adlfjla"; char[] ars = ss.toCharArray(); char x = Character.toUpperCase(ss.charAt(ars.length - 1)); ars[ars.length - 1] = x; String m = new String(ars); System.out.println(m); } public void LT() { String two = "Nature has given us that two ears, two eyes, and but one tongue, to the end that we should hear and see more than we speak"; int lt = two.lastIndexOf("two"); char[] cc = two.toCharArray(); char atwo = Character.toUpperCase(two.charAt(lt)); cc[lt] = atwo; String z = new String(cc); System.out.println(z); } public void RepeatCount() { String[] strings = new String[100]; for (int i = 0; i < strings.length; i++) { strings[i] = randomString(2); } int count = 0; for (String string : strings) { System.out.print(string + " "); count++; if (count % 20 == 0) { System.out.println(); } } String[] repeatstring = new String[100]; int repeattimes = 0; boolean flag = false; for (int i = 0; i < strings.length; i++) { for (int j = 0; j < repeatstring.length; j++) if (strings[i].equals(repeatstring[j])) { flag = true; break; } if (flag) // 如果repeat数组中已经存在该字符串，就终止本次循环 continue; for (int k = i + 1; k < strings.length; k++) { if (strings[i].equals(strings[k])) { repeatstring[repeattimes] = strings[k]; repeattimes++; break; } } } System.out.println("总共有 " + repeattimes + " 种重复的字符串"); if (repeattimes == 0) { System.out.println("没有重复"); } else { System.out.println("分别是："); for (int z = 0; z < repeattimes; z++) { System.out.print(repeatstring[z] + " "); } } } public void StringB() { String tenbit = randomString(10); long x = System.currentTimeMillis(); for (long i = 0; i < 100000; i++) { tenbit += randomString(10); } long y = System.currentTimeMillis(); System.out.println(y-x); StringBuffer tenbit2 = new StringBuffer(randomString(10)); long x2 = System.currentTimeMillis(); for (long i = 0; i < 100000; i++) { tenbit2.append(randomString(10)); } long y2 = System.currentTimeMillis(); System.out.println(y2-x2); } public static void main(String[] args) { Start2 start2 = new Start2(); // start2.Ch(); // start2.RanC(); // start2.RS(); // start2.secret(); // start2.LetterC(); // start2.Rkl(); // start2.GU(); // start2.LW(); // start2.LT(); // start2.RepeatCount(); start2.StringB(); } }