Java Learning-Classroom summary

First, the string comparison method

1) ' = = ' address value comparison
2) equals () method content Comparison

Two instantiation methods of the String class
1) String str= "Hello";
2) string Str=new string ("Hello");

Three
String s= "AA" + "BB" + "CC";
String s= "AABBCC";//Compiler optimizations

Iv. common methods of the string class

1. Publicstring (char[] value) Description: Converts all character array contents into strings

2. Publicstring (char[] value,int offset,int count) Description: Converts a partial character array to a string, offset represents the starting point, and count indicates the length to be manipulated

3. Publicchar charAt (int index) Description: Gets the character at the specified index position

Classroom Programming:

Package Com.cqvie.ceshi;

public class Ceshi {

public static void Main (string[] args) {
Char[] Ch=new char[] {' A ', ' B ', ' C ', ' d ', ' e ', ' f '}; Defining strings
String Str1=new string (ch);
System.out.println (STR1);
String Str2=new string (ch,2,3);
System.out.println (STR2);
Char Str3=str1.charat (3);
System.out.println (STR3);
}
}

Running Result: abcdef

Cde

D

4. Publicint Length () Description: Get string length

Classroom Programming:

Package Com.cqvie.chuan;

public class Chuan {

public static void Main (string[] args) {
String s= "World"; Defining strings
int Str=s.length (); S.length return value for shaping, saved in Str
System.out.println (str);
}
}

Run Result: 5

5. Publicint indexOf (string str) Description: Finds the position of the specified string from scratch, cannot find return-1

Classroom Programming:

Package Com.cqvie.chuan;

public class Chazhao {

public static void Main (string[] args) {
String str= "The weather is fine today";
int S=str.indexof ("weather");
System.out.println (s);

}
}

Run Result: 2

6. Publicint IndexOf (string str,int fromIndex) Description: The position of the string being searched backwards by the specified position, no return-1 found

Classroom Programming:

Package Com.cqvie.chuan;

public class ChaZhao1 {

public static void Main (string[] args) {
String str= "Yesterday Today Tomorrow"; Defining strings
int S=str.indexof ("Day", 1);
System.out.println (s);
int S1=str.indexof ("Day", s+1);
System.out.println (S1);
}

}

Run Result: 1

3

Classroom programming: Querying the position of the 5th "thing" in a string

Package Com.cqvie.chuan;

public class ChaZhao2 {

public static void Main (string[] args) {
String s= "The affairs of the Family matter everything cares about";
int p=-1;
int n=5;
String key= "thing";
for (int i=0;i<n;i++)
{
P=s.indexof (key, p+1);
}
SYSTEM.OUT.PRINTLN (P);
}
}

Run Result: 8

Java Learning-Classroom summary