1 public class Strings {
2
3
4 /**
5 * 重复某个字符
6 * <p>
7 * 例如：
8 * 'a' 5 => "aaaaa"
9 * 'a' -1 => ""
10 *
11 * @param c 被重复的字符
12 * @param count 重复的数目，如果小于等于0则返回""
13 * @return 重复字符字符串
14 */
15 public static String repeat(char c, int count) {
16 char[] a = new char[count];
17 if (count > 0) {
18 for (int i = 0; i < count; i++) {
19 a[i] = c;
20 }
21 }
22 else
23 return null;
24 }
25 String str1 = new String(a); //强转
26 return str1;
27
28
29 }
30 public static String fillafter(String str, char filledChar, int len) {
31 char []charArray = str.toCharArray(); // 利用 toCharArray 方法将STR 字符转换为 字符数组 用char [] ___ (数组名接受)
32 char[]arr=new char[len];
33 if(len<charArray.length){
34 return str;
35 }
36 else{
37 for(int i= 0;i<charArray.length;i++){
38 arr[i]=charArray[i];
39
40 }
41 for(int i=charArray.length;i<len;i++){
42 arr[i]= filledChar;
43 }
44 String Str3 = new String(arr); //强转一定要注意符号的书写；
45 return Str3;
46
47
48 }
49
50 }
51 // 实现在字符串的前面加上字符操作，重点在于对于字符串的的长度在FOR循环里面的掌握
52
53 public static String fillBefore(String str, char filledChar, int len) {
54 char []charArray1 = str.toCharArray();
55 char []array=new char [len];
56 if(len<charArray1.length){
57 return str;
58 }
59 else{
60
61 for(int j = 0, i = len-charArray1.length;i<len;i++,j++){
62 array[i]=charArray1[j];
63 }
64 for(int i = 0;i<len-charArray1.length;i++){
65 array[i]= filledChar;
66 }
67 String Str7 = new String(array);
68 return Str7;
69 }
70
71
72
73
74 }
75 /**
76 * 移除字符串中所有给定字符串
77 * 例：removeAll("aa-bb-cc-dd", "-") => aabbccdd
78 *
79 * @param str 字符串
80 * @param strToRemove 被移除的字符串
81 * @return 移除后的字符串
82 */
83 public static String removeAll(CharSequence str, CharSequence strToRemove) {
84 String Str4= str.toString();
85 String Str5= strToRemove.toString();
86 char []arr1 = Str4.toCharArray();
87 char []arr2 = Str5.toCharArray();
88 String a ="";
89 for(int i =0;i<arr1.length;i++){
90 if(arr1[i]!=arr2[0]){
91 a=a+arr1[i];
92
93 }
94 }
95 return a;
96
97 }
98 // 用第三个元素交换首尾的字符 left ++ right -- 这样就能使得 字符的逆置
99 public static String reverse(String str){
100 char [] arra=str.toCharArray();
101 char [] a = new char [arra.length];
102 int left = 0;
103 int right = arra.length-1;
104 char tmp = '0';
105 while(left<right){
106 tmp = arra[left];
107 arra[left]=arra[right];
108 arra[right]= tmp;
109 left++;
110 right--;
111
112 }
113 String Str6 = new String(arra); //强制转换为String类型
114 return Str6;
115
116 }
117
118
119 public static void main(String[] args) {
120 char a = 'a';
121 int count = 5;
122 char b = 'A';
123 System.out.println(reverse("abcdef"));
124 System.out.println(removeAll("aa-bb-cc","-"));
125 System.out.println(repeat(a,count));
126 System.out.println(fillafter("ABCD", b, 6));
127 System.out.println(fillBefore("ABCD", b, 6));
128
129
130 }
131 }
