Common Operations in the String class

        String s = "java01"      len =  }

          String s1 = "java01"       ch = s1.charAt(3       }

Int indexOf (int ch): returns the location where ch first appears in the string.

Int indexOf (int ch, int fromIndex): searches for the position specified by fromIndex to obtain the position where ch appears in the string.

Int indexOf (String str): returns the position where str first appears in the String.
Int indexOf (String str, int fromIndex): searches for the position specified by fromIndex to obtain the position where str appears in the String.

        String s = "javascript"      x1 = s.indexOf('s'      x2 = s.indexOf('a',2      x3 = s.indexOf("script"      x4 = s.indexOf("script",2     System.out.println("x1="+x1+",x2="+x2+",x3="+x3+",x4="+ }

        String s = "javascript"      x = s.lastIndexOf('a'     System.out.println("x="+}

        String s1 = "javascript"     String s2 = s1.substring(4     String s3 = s1.substring(0,5     System.out.println("s2="+s2+",s3="+ }

 

 

 

Stirng (char [], fffset, count): converts a portion of the character array into a string.

Static String copyValueOf (char []);
Static String copyValueOf (char [], int offset, int count); (offset indicates the start position and count indicates the number. If the length of the character array is exceeded, the character String is out of bounds)

// ValueOf this method can be used not only to convert character arrays into strings, but also to convert other basic data types into strings.
Static String valueOf (char []);
Static String valueOf (char [] data, int offset, int count)

        [] arr ={'j','a','v','a','s','c','r','i','p','t'          String s1 =      String s2 =  String(arr,2,7     System.out.println("s1="+s1+",s2="+      　　     String s3 =     String s4 = String.copyValueOf(arr, 2, 7     System.out.println("s3="+s3+", s4="+ }

 

        String s = "javascript"     [] arr =     (   }

 

Stirng (byte [], fffset, count): convert part of the byte array

        [] arr ={'j','a','v','a','s','c','r','i','p','t'     String s1 =      String s2 =  String(arr,5,6     System.out.println("s1="+s1+",s2="+ }

        String s1 = "javascript"     [] arr =        }

 

Static String valueOf (int)

Static String valueOf (double)

3 + ""; String. valueOf (3); // This is the same

 

        String s1 = "javascript"     String s2 = s1.toUpperCase();     String s3 = s2.toLowerCase();     System.out.println("s2="+s2+",s3="+ }

 

 

 

Judgment:

Special: indexOf (str) Can index the location where str appears for the first time. If-1 is returned, it indicates that the str does not exist in the string. Therefore, it can be used to determine whether the specified method contains the str. This method can be used to determine whether or not the str method exists and obtain the position where it appears.
It is used only for determining the location with contains. You must determine the location and use indexOf

        String s = "javascript"      b = s.contains("java"  }

 

        String s = " ";      b =  }

 

        String s = "Array.java"      b1 = s.startsWith("Array");      b2 =s.endsWith(".java");     System.out.println("b1="+b1+",b2="+ }

 

        String s1 = "javascript"     String s2 = "javascript"     String s3 = "html+CSS"      b1 =      b2 =     System.out.println("b1="+b1+",b2="+ }

 

Comparison between objects uses the compareTo method, while comparison between basic data types uses operators such as greater than signs, smaller than signs, and equal signs.

        String s1 = "javascript"     String s2 = "javascript"     String s3 = "java"      b1 =      b2 =      b3 =     System.out.println("b1="+b1+",b2="+b2+",b3="+ }

 

Other common methods:

String replace (oldchar, newchar); replace one character
String replace (CharSequence target, CharSequence replacement); can replace a String

        String s = "javascript"     String s1 = s.replace('a', 'b'     String s2 = s.replace("java", "php"     System.out.println("s1="+s1+",s2="+ }

 

        String s = "java,javascript,php"     String[] ss = s.split(",");        }

 

        String s = "   javascript     "     String ss  =   }