1.計算一個字符串中各個字符出現的次數:
public class CountCharFromStr {
public static void main(String[] args) {
String str = "abcedsadgsadfasdfaa";
TreeMap<Character,Integer> map=new TreeMap<Character,Integer>();
map=count(str);
for(Entry<Character,Integer> entry:map.entrySet()){
System.err.println(entry.getKey()+"----"+entry.getValue());
}}
public static TreeMap<Character,Integer> count(String str){
char[] arr=str.toCharArray();
TreeMap<Character,Integer> map=new TreeMap<Character,Integer>();
for(char ch:arr){
if(!map.containsKey(ch)){
map.put(ch,1);
}else{
int count=map.get(ch)+1;
map.put(ch, count);}
}
return map;
}
}
結果爲:a----6 b----1 c----1 d----4 e----1 f----2 g----1 s----3
2.截取字符串中的中文:
public class CutChineseFromStr {
public static void main(String[] args) {
String reStr=CutChinese("234實時234將來a,.bnn.dds看df看");
System.out.println("截取的中文爲:"+reStr);
}
public static String CutChinese(String str){
//獲取系統編碼
String encoding=System.getProperty("file.encoding");
StringBuilder result=new StringBuilder();
char[] ch=str.toCharArray();
for(char c:ch){
if(encoding.equals("UTF-8")){
//系統編碼爲UTF-8時一箇中文佔三個字節
if(String.valueOf(c).getBytes().length==3){
result.append(c);
}
}
if(encoding.equals("GBK")){
//系統編碼爲GBK時一箇中文佔三個字節
if(String.valueOf(c).getBytes().length==2){
result.append(c);
}}
}
return result.toString();
}
}
結果爲:截取的中文爲:實時將來看看
3.統計某個字符在字符串出現的個數:
public class CountSpecifyChar {
public static void main(String[] args) {
int count=countChar("sfdwerwerhret",'e');
System.out.println("字符出現的次數爲:"+count);
}
public static int countChar(String str,char c){
int count=0;
char[] arr=str.toCharArray();
for(char ch:arr){
if(ch==c){
++count;}
}
return count;}
}
結果爲:字符出現的次數爲:3
4.判斷一個字符串中子字符串出現的次數:
public class StringContainsSonString {
public static void main(String[] args) {
int result=getCount("wersdsfdswersdfsfwerrsdfwer","wer");
System.out.println("字符串出現的次數爲"+result);
}
public static int getCount(String str,String token){
int count=0;
while(str.indexOf(token)!=-1){
count++;
str=str.substring(str.indexOf(token)+token.length());
}
return count;
}
}
結果爲:字符串出現的次數爲:4