Java Learning Notes

String manipulation:

String split: string array[] = Str.split ("\ t");

List operations:

Define:list<string> list=new ArrayList ();

add element: List.add ("Apple");

Determine if an element is included: List.contains ("Apple")

HashMap Operation:

Defined:

hashmap<string, double> map = new hashmap<string, double> ();

Map.put ("Apple", "1.0");

Determine if Key:map.containsKey ("Apple") is included

Get Key-value:map.get ("apple")

Java Read file:

1. read file contents by line

Package Readfile;import Java.io.bufferedreader;import Java.io.BufferedWriter;
Import Java.io.File;
Import java.io.FileNotFoundException;
Import Java.io.FileReader;
Import Java.io.FileWriter;
Import java.io.IOException;

 Public classMain { Public Static voidMain (string[] args) throws filenotfoundexception,ioexception{FileReader reader=NewFileReader ("Resource/test.txt"); Input path BufferedReader br=NewBufferedReader (reader); String Str=NULL;  while(str = br1.readline ())! =NULL) {System.Out.println (str); }
Br.close (); }}

JAVA Write file

 PackageWriteFile;ImportJava.io.BufferedReader;ImportJava.io.BufferedWriter;ImportJava.io.File;Importjava.io.FileNotFoundException;ImportJava.io.FileReader;ImportJava.io.FileWriter;Importjava.io.IOException; Public classMain { Public Static voidMain (string[] args)throwsfilenotfoundexception,ioexception{bufferedwriter writer=NewBufferedWriter (NewFileWriter (NewFile ("Resource/wt.txt")) ;//write path
FileWriter writer = new FileWriter ("Resource/wt.txt");//This method can also Writer.write ("Hello\tworld\r\n"); Writer.close ()}}

PS: If you want to enter new content that does not overwrite the contents of the file, change

BufferedWriter writer = new BufferedWriter (new FileWriter (New File ("Resource/wt.txt", true));

FileWriter writer = new FileWriter ("Resource/wt.txt", true);

Java Learning Notes