Java Basic Rules
AD MOB
// file name MyFirstClass.java
import java.util.*;
import java.lang.Math;
import java.io.*;
import javax.swing.*;
public class MyFirstClass{ // start of program
public static void main(String[] args) { // basic function main
// variables and calculation
int a=2;
int b=3;
int c=Integer.parseInt(JOptionPane.showInputDialog(" Put number: ", "1"));
System.out.println("Number is: "+c);
System.out.println(a+" * "+b+" = "+(a*b));
System.out.println("a^3 "+Math.pow(a,b));
//array
int[] array_my=new int[10];
array_my[0]=3;
array_my[1]=5;
System.out.println("Number of elements "+array_my.length+" 1 + 2 element of array "+(array_my[0]+array_my[1]));
//strings
String txt="Quick red fox";
String txt2=JOptionPane.showInputDialog("Write text: ", "word");
System.out.println("Text is: "+txt2);
String[] count_of_word=txt.split(" ");
System.out.println("Length: "+txt.length()+" Count of words "+count_of_word.length);
System.out.println(txt +" -> "+txt.replace("red","brown"));
System.out.println("First 5 chars of string is: "+ txt.substring(0,5));
//for a if
for(int i=0; i<10;i++){
if(i==3)System.out.println("i equal "+i);
}
// file
try {
File soubor=new File("some_file.txt");
if(!soubor.exists()){
System.out.println("File dont exist");
}
else { // utf-8 encoding
BufferedReader in1 = new BufferedReader(new InputStreamReader(new FileInputStream(soubor),"UTF-8"));
BufferedWriter out1 = new BufferedWriter(new OutputStreamWriter(new FileOutputStream("zapis.txt"),"UTF-8"));
String str;
while ((str = in1.readLine())!=null){
System.out.println(str);
out1.write(str+"
");
}
in1.close();
out1.close();
}
} catch(IOException e){System.out.println("Error " + e);}
// dir
File pathName = new File("some_dir");
String[] fileNames = pathName.list();
if(pathName.exists())
System.out.println("Name of first file in "some_dir": "+fileNames[0]);
else System.out.println("dir not exist");
//function
int nResult = calculateMyFc(3,5);
System.out.println("Result of function: "+nResult);
} // end of function main
// new function , you can add to end MyFc = my function
public static int calculateMyFc(int a, int b){
return (a+b);
}
} // end of class of program
396LW NO topic_id
AD
Další témata ....(Topics)
If you change the package name, you have to add new package name in:
DictionaryProvider.java
Do not forget change package name in all java class and xml/searchable.xml
In my project I changed like this:
DictionaryProvider.java
public class DictionaryProvider extends ContentProvider {
String TAG = "DictionaryProvider";
// public static String AUTHORITY = "com.example.android.searchabledict.DictionaryProvider";
// change to your new package name
public static String AUTHORITY = "com.myweb.mysubdomen.searchabledict.DictionaryProvider";
public static final Uri CONTENT_URI = Uri.parse("content://" + AUTHORITY + "/dictionary");
// in AndroidManifest.xml
//change com.example.android to your package e.g. com.myweb.mysubdomen
<!-- Provides search suggestions for words and their definitions. -->
<provider android:name="com.example.android.searchabledict.DictionaryProvider"
android:configChanges="keyboard|keyboardHidden|orientation"
android:authorities="com.example.android.searchabledict.DictionaryProvider" />
<!-- Points to searchable activity so the whole app can invoke search. -->
<meta-data android:name="android.app.default_searchable"
android:configChanges="keyboard|keyboardHidden|orientation"
android:value=".SearchableDictionary" />
// I change like this:
<!-- Provides search suggestions for words and their definitions. -->
<provider android:name=".DictionaryProvider"
android:configChanges="keyboard|keyboardHidden|orientation"
android:authorities="cz.okhelp.android.searchabledict.DictionaryProvider" />
<!-- Points to searchable activity so the whole app can invoke search. -->
<meta-data android:name="android.app.default_searchable"
android:configChanges="keyboard|keyboardHidden|orientation"
android:value=".SearchableDictionary" />
Do not forget change package name in all java class and xml/searchable.xml
In my project I changed like this:
<searchable xmlns:android="//schemas.android.com/apk/res/android"
android:label="@string/search_label"
android:hint="@string/search_hint"
android:searchSettingsDescription="@string/settings_description"
android:searchSuggestAuthority="cz.okhelp.android.searchabledict.DictionaryProvider"
android:searchSuggestIntentAction="android.intent.action.VIEW"
android:searchSuggestIntentData="content://cz.okhelp.android.searchabledict.DictionaryProvider/dictionary"
android:searchSuggestSelection=" ?"
android:searchSuggestThreshold="1"
android:includeInGlobalSearch="true"
>
</searchable>
Issue: After after renaming package this problem occurred "R cannot be resolved to a variable".
Solution: Try Clean your project Project » Clean » Clean projects selected below » select your project and click OK.
Try to delete the invalid code and type it again:
Solution: Try Clean your project Project » Clean » Clean projects selected below » select your project and click OK.
Try to delete the invalid code and type it again:
LinearLayout layout = (LinearLayout) findViewById(R.id.layout); // delete R.id.layout
LinearLayout layout = (LinearLayout) findViewById();
LinearLayout layout = (LinearLayout) findViewById(R.id.layout); // re-write this code R.id.layout
Google Android example source code - is text changed in EditText ?
EditText hEditText;
// TextChanged in onCreate
hEditText = (EditText)findViewById(R.id.idEditText);
hEditText.addTextChangedListener(new TextWatcher() {
public void afterTextChanged(Editable str) {
}
public void beforeTextChanged(CharSequence s, int start, int count,
int after) {
}
public void onTextChanged(CharSequence sq, int start, int before,
int count) {
}
});
String s = "AbcČ";
String s2 = s.toLowerCase(new Locale("cs_CZ")); // Czech Republic
String s3 = s.toLowerCase(new Locale("de_DE")); // Germany
//
en_US
en_GB
ar_EG
be_BY
bg_BG
ca_ES
cs_CZ
da_DK
de_DE
int occupy 4 bytes (32 bits) in memory
int in Java example of using Integer and Array of Integer and Iteger to String
int in Java example of using Integer and Array of Integer and Iteger to String
// get max end min values of int in Java example 4 bytes (32 bits) PC architecture
System.out.println(Integer.MAX_VALUE); // 2147483647
System.out.println(Integer.MIN_VALUE); // -2147483648
// members variable
private int mProgress = 10;
//integer to string java
int myInteger = 8;
String myString = Integer.toString(myInteger);
// a final variable can only be initialized once
static final int NUM_PARTICLES = 15;
for (int i = 0; i < NUM_PARTICLES ; i++) {
// do something
}
// int as return value of function
public int getCount() {
return 5;
}
// int as a parametr of function
public float getFloatFromInt(int i) {
float fRet = (float) i;
return fRet;
}
//array of int
int[] anArray; // declares an array of integers
anArray = new int[2]; // allocates memory for 2 integers
anArray[0] = 100; // initialize first element
anArray[1] = 200; // initialize second element
for (int i = 0; i < anArray.length; i++) {
// print out values from anArray
System.out.println("Index: " + i);
System.out.println("Value: " + anArray[i]);
}
Editace: 2013-12-09 11:06:19
Počet článků v kategorii: 396
Url:java-basic-rules
AD
