Summary of common USES of String in Java
- 2020-04-01 02:24:19
- OfStack
1 > To obtain
1.1: the number of characters contained in a string, that is, the length of the string.
Int length(): gets the length
1.2: get a character in a position according to the position.
Char charAt (int index)
1.3: gets the position of the character in the string based on the character.
Int indexOf(int ch): returns the first occurrence of the ch in the string.
Int indexOf(int ch,int fromIndex): gets the position where the ch appears in the string, starting with the position specified by fromIndex.
Int indexOf(String STR): returns the first occurrence of STR in a String.
Int indexOf(String STR, int fromIndex): gets the position where STR appears in the String, starting with the position specified by fromIndex.
1.4: int lastIndexOf(String STR): reverse index.
2 > judge
2.1: whether a substring is included in the string.
Boolean contains (STR);
Special: indexOf(STR): can index STR until it appears for the first time. If it returns -1, it does not exist in the string.
Therefore, it can also be used to determine whether to include a given.
If (STR) indexOf (" a ")! = 1)
And this method can not only determine, but also obtain the location of the occurrence.
2.2: whether there is content in the string.
Boolean isEmpty(): the principle is to determine if the length is 0.
2.3: whether the string begins with the specified content.
Boolean startsWith (STR);
2.4: whether the string ends with the specified content.
Boolean endsWith (STR);
2.5: to determine whether the character content is the same, the equals method in the object class is copied.
Boolean equals (STR);
2.6: determine if the content is the same and ignore case.
Boolean. EqualsIgnorecase ();
3 > conversion
3.1: converts an array of characters into a string.
Constructor: String(char[])
String(char[],offset,count): converts a portion of the array of characters into a String
Static method:
The static String copyValueOf (char []);
Static String copyValueOf(char[] data,int offset,int count);
The static String the valueOf (char []);
3.2: converts a string to a group of characters
Char [] tocharArray ();
3.3: converts a byte array into a string.
String (byte [])
String(byte[],offset,count): converts a portion of the byte array into a String
3.4: converts a string to a byte array.
Byte [] getBytes ()
3.5: converts basic data types into strings,
The static String the valueOf (int)
The static String the valueOf (double)
// 3+"" is the same value as string.valueof (3)
Special: strings and byte arrays can be encoded during conversion.
4 > replace
String replace (oldchar, newchar);
5 > cutting
The split String [] (regex);
6 > The substring. Gets a portion of a string
String subString (begin);
String subString (begin and end);
7 > Convert, remove Spaces, compare.
7.1: converts a string to uppercase or lowercase
String toUpperCsae() large to small
String toLowerCsae() turns small to large
7.2: removes multiple Spaces from both ends of the string
String trim ();
7.3: compare the two strings in their natural order
Int compareTo (string);
Please take a look at the following code. The following codes are all for the above seven USES of string.
class StringMethodDemo
{
public static void method_Zhuanhuan_Qukong_Bijiao()
{
String s = " hello Java ";
//The print result is :(both hello and Java front and back doors have Spaces) hello Java
sop(s.toUpperCase());
//The print result is :(both HELLO and JAVA front and back doors have Spaces) HELLO JAVA
sop(s.toLowerCase());
//Print and the result: "hello Java" without Spaces
sop(s.trim());
//Capital of the comparison number, print: 1, because b corresponds to the ASCII value of 98,
//A corresponds to 97, so b minus a is equal to 1
String s1 = "abc";
String s2 = "aaa";
sop(s1.compareTo(s2));
}
public static void method_sub()
{
String s = "abcdef";
//The print result is: cdef, starting at the specified location and ending at the specified location. If the corner mark does not exist, the string corner mark overbounds.
sop(s.substring(2));
//The print result is: CD, including the head, not the tail.
sop(s.substring(2,4));
}
public static void method_split()
{
String s = "zhangsan,lisi,wangwu";
String[] arr = s.split(",");
for(int x=0; x<arr.length; x++)
{
sop(arr[x]);
}
}
public static void method_replace()
{
String s = "hello java";
//String s1 = s.replace('a','n');
//String s1 = s.r eplace (' w ', 'n'); If the character to be replaced does not exist, the original string is returned
String s1 = s.replace("java","world");//The print result is: hello world
sop("s="+s); //The print result is: hello Java because once the string is initialized, the value cannot be changed
sop("s1="+s1);//The print result is: hello JNVN
}
public static void method_trans()
{
char[] arr = {'a','b','c','d','e','f'};
String s = new String(arr,1,3);
sop("s="+s);//The print result is: BCD
String s1 = "zxcvbnm";
char[] chs = s1.toCharArray();
for(int x=0; x<chs.length; x++)
{
sop("ch="+chs[x]);//The print result is: ch=z, x,c,v,b,n,m
}
}
public static void method_is()
{
String str = "ArrayDemo.java";
//Determines if the file name is the beginning of the Array word
sop(str.startsWith("Array"));
//Determines if the file name is a.java file
sop(str.endsWith(".java"));
//Determines whether Demo is included in the file
sop(str.contains("Demo"));
}
public static void method_get()
{
String str = "abcdeakpf";
//The length of the
sop(str.length());
//Gets a character by index
sop(str.charAt(4));
//SOP (STR) charAt (40)); When accessing to the Angle of the string does not exist in the StringIndexOutOfBoundsException happens (string Angle the cross-border exception)
//Gets the index by character
//sop(str.indexOf('a'));
sop(str.indexOf('a',3));//It's 5, because 3 is d,
//So we're going to look for a after d, and the fifth Angle is a
//SOP (STR. IndexOf ('t',3)) print: -1, return -1 if no corner mark is found
//Reverse index the position where a character appears (look from right to left, but the corner marks still start from left)
sop(str.lastIndexOf("a"));
}
public static void main(String[] args)
{
method_Zhuanhuan_Qukong_Bijiao();
//method_sub();
//method_split();
//method_replace();
//method_trans();
//method_is();
//method_get();
/*
String s1 = "abc";
String s2 = new String("abc");
String s3 = "abc";
System.out.println(s1==s2);
System.out.println(s1==s3);
*/
}
public static void sop(Object obj)
{
System.out.println(obj);
}
}