Java：String、StringBuilder、reverse反转、append拼接、遍历、统计

import java.util.Scanner;  /* * Scanner:用于获取键盘录入数据 * public String nextline():获取键盘录入字符串数据 */  public class ScannerLearn {     public static void main(String[] args) {         Scanner sc = new Scanner(System.in);         System.out.println(请输入数据：);         String line = sc.nextLine();         System.out.println(您输入的数据是：+line);  /* * String构造方法 * public String（） 创建空白字符串对象 * public String（char[] chs） 根据字符数组的内容，来创建字符串对象 * public String（byte[] bys） 根据字节数组的内容，来创建字符串对象 * String s = abc 直接赋值（推荐使用）*/         String s1 = new String();         System.out.println(s1：+s1);  //s1：          char [] chs = {'a','b','c'};         String s2 = new String(chs);         System.out.println(s2：+s2); //s2：abc          byte[] bys = {97,98,99};  //97字节底层对应的就是a         String s3 = new String(bys);         System.out.println(s3：+s3); //s3：abc          //以下存储内存地址不一样         String s4 = new String(chs);         String s5 = new String(chs);          //以下存储内存地址一样         String s6 = abc;         String s7 = abc;          //比较的为地址值         System.out.println(s4==s5); //false         System.out.println(s6==s7); //true         System.out.println(s4==s6); //false          //比较数据值         System.out.println(s4.equals(s5)); //true         System.out.println(s6.equals(s7)); //true         System.out.println(s4.equals(s6)); //true          //遍历字符串         String name = YinRuMin;         for(int i=0;i<name.length();i++){             System.out.println(name.charAt(i));         }          //统计字符次数，大小写和数字分别统计         //Scanner ss = new Scanner(System.in);         System.out.println(请输入字符串：);         String word = sc.nextLine();         int uw = 0;         int lw = 0;         int dig = 0;         for(int i=0;i<word.length();i++){             if(word.charAt(i)>='A'&&word.charAt(i)<='Z'){                 uw+=1;             }else if(word.charAt(i)>='a'&&word.charAt(i)<='z'){                 lw+=1;             }else if(word.charAt(i)>='0'&&word.charAt(i)<='9'){                 dig+=1;             }         }         System.out.println(大写字母有：+uw+个);         System.out.println(小写字母有：+lw+个);         System.out.println(数字字符有：+dig+个);          //StringBuild         StringBuilder sb = new StringBuilder();         System.out.println(sb:+sb);         System.out.println(sb.length():+sb.length());          StringBuilder sb2 = new StringBuilder(abdcdd);         System.out.println(sb2:+sb2);         System.out.println(sb2.length():+sb2.length());          StringBuilder sb3 = sb2.append(eee);         System.out.println(sb2:+sb2); //sb2:abdcddeee         System.out.println(sb3:+sb3); //sb2:abdcddeee         System.out.println(sb2==sb3);  //true          sb.append(100);         sb.append(yin);         sb.append(xxx);         System.out.println(sb:+sb); //sb:100yinxxx         sb.append(22).append(ccc).append(fff); //链式拼接         System.out.println(sb:+sb); //sb:100yinxxx22cccfff          sb.reverse();  //反转         System.out.println(sb:+sb); //sb:fffccc22xxxniy001          //String转换为StringBuilder         String sb6 = Iverson;         StringBuilder sb7 = new StringBuilder(sb6);         System.out.println(sb7:+sb7);          //StringBuilder转换为String         StringBuilder sb4 = new StringBuilder();         sb4.append(Iverson);         //String sb5 = sb4;错误方法         String sb5 = sb4.toString();         System.out.println(sb5:+sb5);           //拼接字符串         int[] arr = {1,2,3,4,5,6};         String s = arrayToString(arr);  //普通拼接         System.out.println(s:+s); //s:[1, 2, 3, 4, 5, 6]         String sb8 = arrayToString2(arr); //StringBuilder拼接         System.out.println(sb8:+sb8); //sb8:[1,2,3,4,5,6]     }     public static String arrayToString(int[] arr){         String s = ;         s +=[;         for(int i = 0;i<arr.length;i++){             if (i==arr.length-1){                 s+=arr[i];             }else {                 s+=arr[i];                 s+=, ;             }         }         s+=];         return s;     }      public static String arrayToString2(int[] arr){         StringBuilder s = new StringBuilder();         s.append([);         for(int i = 0;i<arr.length;i++){             if (i==arr.length-1){                 s.append(arr[i]);             }else {                 s.append(arr[i]).append(,);             }         }         s.append(]);         String sb = s.toString();         return sb;     } }