String类的几个小总结 - 黑马程序员技术交流社区

package String类小练习;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;
public class MyTrim {
public static void main(String[] args) {
String s1 = " akkcdehellowaskkjdl ";
String s2 = "cshellowds";
System.out.println(myTrim(s1));
System.out.println(myReverse(s1));
System.out.println(getSubCount(s1,"kk"));
System.out.println(getMaxSubStr(s1,s2));
getCharCoutInStr(s1);
}
//去除字符串两端的空格
public static String myTrim(String s)
{
int start = 0;
int end = s.length()-1;
while(start < end && s.charAt(start)==' ')
start++;
while(start < end &&s.charAt(end)==' ')
end--;
String newStr = s.substring(start,end+1);
return newStr;
}
//翻转字符串
public static String myReverse(String s)
{
String newStr = new String();
char [] chs = s.toCharArray();
for(int i=chs.length-1;i>=0;i--)
{
newStr+=chs[i];
}
return newStr;
}
//获取一个字符串在另一字符串中出现的次数
public static int getSubCount(String s,String key)
{
int count = 0;//计数器，记录每次出现的次数
int index = 0;//记录每次出现的角标位置
while((index =s.indexOf(key))!=-1)
{
count++;
s = s.substring(index+key.length(),s.length());
}
return count;
}
//获取两个字符串中相同的最大子串
public static String getMaxSubStr(String s1,String s2)
{
String maxStr = new String();
String max = (s1.length()>s2.length())?s1:s2;
String min = (max == s1)?s2:s1;
for(int i=0;i<min.length();i++)
{
for(int start = 0,end = min.length()-1;end!=min.length()+1;start++,end--)
{
maxStr = min.substring(start,end);
if(max.contains(maxStr))
{
return maxStr;
}
}
}
return null;
}
//获取字符在字符串出现的次数
public static void getCharCoutInStr(String s)
{
int count = 0;
Map<Character, Integer> mp = new TreeMap<Character, Integer>();
char [] chs = s.toCharArray();
for(int i = 0;i<chs.length;i++)
{
if(chs[i]>='a'&&chs[i]<='z'||chs[i]>='A'&&chs[i]<='Z')
{
if(!mp.containsValue(chs[i]))
{
mp.put(chs[i], 1);
}
else
{
count = mp.get(chs[i])+1;
mp.put(chs[i], count);
}
}
}
//取出集合中的元素
Set<Character> keySet = mp.keySet();
Iterator<Character> it = keySet.iterator();
while(it.hasNext())
{
Character key = it.next();
Integer value = mp.get(key);
System.out.print(key+"("+value+")");
}
}
}

复制代码