1.charAt(int index)
String s = "1234567890";
System.out.println(s.charAt(1)); //2
2.compareTo(String anotherString)
String s1 = "1234567870";
String s2 = "12345678";
String s3 = "1234567891";
System.out.println(s1.compareTo(s2)); //2 返回長度差
System.out.println(s1.compareTo(s3)); //-2 返回最前一位不同值的差‘7’-‘9’
3.concat(String str) 與‘+’類似，連接字符串
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endsWith(String str)是否以str結(jié)尾
startsWith(String str)和startsWith(String str , int offset)
5.equals(String str) equalsIgnoreCase(String str)判斷是否相等
int indexOf(char ch)
int indexOf(char ch ,int fromIndex)
int indexOf(String str)
int indexOf(String str ,int fromIndex)
int lastIndexOf(char ch)
int lastIndexOf(char ch ,int fromIndex)
int lastIndexOf(String str)
int lastIndexOf(String str ,int fromIndex)
String str = new String("skljfkjklsaaifs");
System.out.println(str.lastIndexOf('s')); //14
System.out.println(str.lastIndexOf('s',10)); //9
length()
replace(char ch1,char ch2)將所有的ch1替換成ch2
replaceAll(String regex,String newstr)
replaceFirst(String regex,String newstr)
String str = new String("a12djhjk7890a");
System.out.println(str.replace('a','q')); //q12djhjk7890q
System.out.println(str.replaceAll("\\d","q")); //aqqdjhjkqqqqa
System.out.println(str.replaceFirst("\\d","q")); //aq2djhjk7890a
String substring(int beginIndex)
String substring(int beginIndex,int endIndex)返回子字符串
char[] toCharArray()
12.toUpperCase()
toLowerCase()
13.String.valueOf(X x)將其他類型轉(zhuǎn)化為String類型
StringBuffer是線程安全的，StringBuilder是線程不安全的，故性能相對較快。具體的使用可查閱API。
StringBuilder sb = new StringBuilder();
sb.append("java"); //sb= "java"
sb.insert(0,"hello "); //sb = "hello java"
sb.replace(5,6,",");//sb = "hello,java"
sb.delete(5,6);//sb = "hellojava"
System.out.println(sb);
sb.reverse(); //sb = "avajolleh"
System.out.println(sb);
System.out.println(sb.length());//9
System.out.println(sb.capacity());//16
sb.setLength(5); //sb = "avajo"
System.out.println(sb);
