String笔记

String string = new String("Hello World!");

replace('e', '*')

//替换字符串
String newStr = string.replace('e', '*')；

charAt(int x)

//求字符串某一位置字符,下标从0开始
char ch = string.charAt(4);//ch =o

substring(int[] args)

//提取子串,下标从0开始
String str1 = str1.substring(1);//str2 = "ello World"
String str2 = str1.substring(1,5);//str3 = "ello"

length()

//求字符串长度
int strlength = string.length();//strlength = 11

toCharArray()

 //返回一个char数组
char[] s = string.toCharArray();

contains(String x)

//字符串string是否包含子字符串s
boolean is = string.contains("llo");  //is=true

split(",")

//字符串切割
String str = "ab,cd,ef";
String[] strList = str.split(",");

trim()

//去除首尾空格
String str = "  aa  ";
str = str.trim();  //str="aa"

indexOf("l")&lastIndexOf("l")

//获取字符所在下标
int num1 = string.indexOf("l"); // ==2

int num1 = string.lastIndexOf("l"); // ==3

toLowerCase()&toUpperCase()

 //字符串换为=全小写=与=全大写=
string = string.toLowerCase();  //小写
string = string.toUpperCase();  //大写StringTokenizer

StringBuilder(线程不安全，效率高)&StringBuffer(线程安全，效率低)

 //StringBuilder() -->线程不安全，效率高
 //StringBuffer() -->线程安全，效率低

 StringBuilder sb = new StringBuilder();  //字符数组长度初始为16
 sb.append(true);  //sb=="true"  两个对象拼接为字符串
 sb.delete(3,5);  //删除，包头不包尾
 sb.reverse();  //字符串反转

分割字符串的3种方式

1. split（）
2. StringTokenizer()

   //把字符串按某个符号分割
   StringTokenizer tokenizer = new StringTokenizer("1-2-3-4-5-6", "-");
   while (tokenizer.hasMoreTokens()) {
           System.out.println(tokenizer.nextToken());
   }

3. 正则表达式

   //把字符串按数字分割出来
   String string = "aa232**ssdd234%sds888";
   String[] arrs = string.split("\\d+");

StringTokenizer