String类
public static void main(String[] args) throws UnsupportedEncodingException {
String str = "你要悄悄学python惊艳所以人! pythonNB.mp4";
//使用字符串api来处理字符串
//1. 获得长度 length():int
System.out.println( str.length() );
//2. 获得指定下标处的字符 charAt(int index):char
System.out.println( str.charAt(1) );
//3. 查看字符串中时候包含 指定字符串内容 contains(String str):boolean
System.out.println( str.contains("python") );
//4.把字符串转出字符数组 toCharArray():char[]
char[] chs= str.toCharArray();
System.out.println( Arrays.toString(chs) );
//5. 查询指定字符串的首次出现的下标 indexOf(String str):int
System.out.println( str.indexOf("py") );
// 从指定位置后查找
System.out.println( str.indexOf("py", 8));
// 反向查找
System.out.println( str.lastIndexOf("py") );
// 反向查找，从指定位置前
System.out.println( str.lastIndexOf("py", 18) );
//6 去除字符串两端的空格 trim():String
System.out.println(str.trim() );
//7 把小写转成大写 toUpperCase():String
System.out.println( str.toUpperCase() );
//8 大写转小写 toLowerCase():String
System.out.println( str.toLowerCase() );
//9 判断字符串是否以某个字符串结尾 endsWith( String s ):boolean
System.out.println( str.endsWith( "mp4" ) );
//10 判断字符串是否以 某个字符串开始 startsWith(String s):boolean
System.out.println( str.startsWith("你") );
//11.替换字符 replace(char oldChar, char newChar):String
System.out.println( str.replace('你', '我') );
// replace(String str, String str2):String
System.out.println( str.replace("python", "java") );
String ss = "abcdefg12mly3s5";
//正则：用一个模式去匹配字符串是否符合这个规则 replaceAll(String reg, String newStr):String
System.out.println( ss.replaceAll("[a-z]", "*") );
//13 字符串拆分 split(String reg):String[]
String mm = "刘德华,歌手,50,香港";
String[] info = mm.split(",");
System.out.println( info[0] );
// 14 字符串截取
System.out.println( str.substring(5) );
System.out.println( str.substring(5, 10));
// 15 字符串编码解码问题【防止乱码编码一致】
String dd = "奥利给";
byte[] bs = dd.getBytes();//[-80, -62, -64, -5, -72, -8]
byte[] bs = dd.getBytes("UTF-8");//[-27, -91, -91, -27, -120, -87, -25, -69, -103]
System.out.println(Arrays.toString(bs) );
//编码
byte[] bbs = {-27, -91, -91, -27, -120, -87, -25, -69, -103};
String sss = new String(bbs, "utf-8");
}