String类总结
1. String类的构造方法
public String(byte[] bytes);
public String(byte[] bytes,int offset,int length);
public String(char[] value);
public String(char[] value,int index,int count);
2. String类的判断功能
boolean equals(Object obj); 比较的是内容
boolean equalsIgnoreCase(String str);
boolean contains(String str);
boolean startsWith(String str);
boolean endsWith(String str);
boolean isEmpty();
3.String类的获取功能
int length();
charAt(int index);
int indexOf(int ch):返回指定字符在此字符串中第一次出现的索引
int indexOf(String str)
int indexOf(int ch,int fromIndex)
int indexOf(String,int fromIndex);
String substring(int start)
String substring(int start,int end)
4.String类的转换功能
byte[] getBytes():转换为字节数组
char[] toCharArray():把字符串转换为字符数组
static String valueOf(char[] chs) :把字符数组转换为字符串
static String valueOf(int i):把int类型转换为字符串
String toLowerCase
String toUpperCase
String concat(String str)
5.String类的其他功能
String replace(char old,char new)
String replace(String old,String new)
String trim()
int compareTo(String str):按照字典顺序比较
int comparetoIgnoreCase(String str)
习题:在大串中统计小串出现的次数
1 package hello; 2 3 import java.io.BufferedOutputStream; 4 import java.io.File; 5 import java.io.FileInputStream; 6 import java.io.FileNotFoundException; 7 import java.io.FileOutputStream; 8 import java.io.IOException; 9 import java.io.InputStreamReader; 10 import java.io.OutputStreamWriter; 11 import java.text.SimpleDateFormat; 12 import java.util.Date; 13 import java.util.HashSet; 14 import java.util.Random; 15 import java.util.TreeSet; 16 17 public class Test02{ 18 public static void main(String[] args) throws Exception { 19 String big="helloworldjavawewillgotherejavaandjava"; 20 String small="java"; 21 int count=0; 22 int index; 23 while((index=big.indexOf(small))!=-1){ 24 count++; 25 big=big.substring(index+small.length()); 26 } 27 System.out.println(count); 28 } 29 }