Java
Regular expressions
1 /*
2 javac TesteRe.java
3 java -cp . TesteRe
4 */
5 /*
6 gcj -C TesteRe.java # compile with gcj, GNU compiler for Java
7 gij -cp . TesteRe # run with gij, GNU interpreter for Java
8
9 Linux executable
10 gcj --main=TesteRe -g -o TesteRe TesteRe.java
11 ldd TesteRe
12 ./TesteRe
13 */
14
15 import java.util.regex.Pattern;
16 import java.util.regex.Matcher;
17
18 public class TesteRe{
19
20 public static void main(String args[]){
21 String values[]={"aa12.txt","a123sss.txt","bs11bb.txt","123aaaa.sql","a12.txt","aaaa12","20ghj","6657"};
22 Pattern a = Pattern.compile("^(\\D+)(\\d+)(\\D+)$");
23 Pattern b = Pattern.compile("^(\\d+)(\\D+)$");
24 Pattern c = Pattern.compile("^(\\D+)(\\d+)$");
25 Pattern d = Pattern.compile("^(\\d+)$");
26
27 for(String item:values){
28 Matcher ma = a.matcher(item);
29 Matcher mb = b.matcher(item);
30 Matcher mc = c.matcher(item);
31 Matcher md = d.matcher(item);
32
33 if(ma.matches()){
34 int val = Integer.parseInt(ma.group(2)) + 1;
35 System.out.println(String.format("A: mv %s %s%d%s",item,ma.group(1),val,ma.group(3) ) );
36 }
37
38 if(mb.matches()){
39 int val = Integer.parseInt(mb.group(1)) + 1;
40 System.out.println(String.format("B: mv %s %d%s",item, val , mb.group(2) ) );
41 }
42
43 if(mc.matches()){
44 int val = Integer.parseInt(mc.group(2)) + 1;
45 System.out.println(String.format("C: mv %s %s%d",item,mc.group(1),val ) );
46 }
47
48 if(md.matches()){
49 int val = Integer.parseInt(md.group(1)) + 1;
50 System.out.println(String.format("D: mv %s %d",item, val ) );
51 }
52
53 }
54 }
55 }
Server/client
Server
1 import java.net.ServerSocket;
2 import java.net.Socket;
3 import java.lang.Thread;
4 import java.util.Stack;
5
6 public class SocketServer{
7 public static void main(String []args){
8 ServerSocket ss = null;
9 int nrThreads= Runtime.getRuntime().availableProcessors() * 2;
10 System.out.println("Nr cores:" + nrThreads);
11 ConnHandler[] c = new ConnHandler[nrThreads];
12 for(int i=0;i<nrThreads;i++){
13 c[i]=new ConnHandler();
14 c[i].start();
15 }
16
17 try{
18 ss = new ServerSocket(1234);
19 ss.setReuseAddress(true);
20 }
21 catch(Exception ex){ }
22 long count=0;
23 while(true){
24 try{
25 Socket s = ss.accept();
26 s.setSoLinger(true,0);
27 int idx = (int)count%nrThreads;
28 c[ idx ].addSocket(s);
29 count++;
30
31 }
32 catch(Exception ex){
33 System.out.println(ex.getMessage());
34 }
35 }
36 }
37 }
1 import java.net.ServerSocket;
2 import java.net.Socket;
3 import java.lang.Thread;
4 import java.util.Stack;
5
6 public class ConnHandler extends Thread{
7 private byte[] rx;
8 private Stack stack;
9 long tid;
10
11 public ConnHandler(){
12 this.rx= new byte[1024];
13 this.stack = new Stack();
14 }
15
16 public void addSocket(Socket s){
17 this.stack.push(s);
18 }
19
20 public void run(){
21 this.tid = Thread.currentThread().getId();
22
23 while(true){
24 if( this.stack.empty() == false){
25 Socket s = (Socket)this.stack.pop();
26 try{
27 if( s.getInputStream().available() > 0 ){
28 int readedBytes = s.getInputStream().read( rx );
29 System.out.println("ThreadId:"+tid + " ReadedBytes:"+ readedBytes +
30 " StackSize:" + this.stack.size() );
31 }
32 s.close();
33 }
34 catch(Exception ex){
35 }
36 }
37 else{ try{ Thread.sleep(500); }catch(Exception ex){} }
38 }
39 }
40 }
Client (python)
1 import threading
2 import time
3 import socket
4
5 class Client (threading.Thread):
6 def __init__(self):
7 threading.Thread.__init__(self) #required
8
9 def run(self):
10 for x in range(1,100):
11 HOST = 'localhost'
12 PORT = 1234
13 s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
14 print('connecting...')
15 s.connect((HOST, PORT))
16 print('sending config...')
17 s.send('test\r\n')
18 s.close()
19 print('complete')
20
21 if __name__=='__main__':
22 clients=[]
23 for x in range(1,100):
24 clients.append( Client() )
25 for c in clients:
26 c.start()
JAVA_TOOL_OPTIONS
Since the command-line cannot always be accessed or modified, for example in embedded VMs or simply VMs launched deep within scripts, a JAVA_TOOL_OPTIONS variable is provided so that agents may be launched in these cases.
- set JAVA_TOOL_OPTIONS=-Dfile.encoding=utf8
- export JAVA_TOOL_OPTIONS=-Dfile.encoding=utf8
http://docs.oracle.com/javase/7/docs/platform/jvmti/jvmti.html#tooloptions
Access private field via reflection
Generate Javadoc using command line
dir /s /b *.java > javafiles.txt
- javadoc -encoding UTF-8 -d docs @javafiles.txt
To add an overview file add -overview overview.html
Java keystore public private keys
keytool -genkey -alias test1rsa -storetype PKCS12 -keyalg RSA -keysize 2048 -keystore keystore1.p12 -validity 3650 Enter keystore password: Re-enter new password: What is your first and last name? [Unknown]: What is the name of your organizational unit? [Unknown]: What is the name of your organization? [Unknown]: What is the name of your City or Locality? [Unknown]: What is the name of your State or Province? [Unknown]: What is the two-letter country code for this unit? [Unknown]: Is CN=Unknown, OU=Unknown, O=Unknown, L=Unknown, ST=Unknown, C=Unknown correct? [no]: yes keytool -list -v -keystore keystore1.p12 -storetype pkcs12
1 /*
2 javac keypair.java
3 java -classpath . keypair
4 */
5 import java.security.KeyStore;
6 import java.security.PrivateKey;
7 import java.security.PublicKey;
8 import java.security.Key;
9 import java.security.cert.Certificate;
10 import javax.crypto.Cipher;
11 import javax.crypto.CipherOutputStream;
12 import java.io.ByteArrayOutputStream;
13 import java.io.FileOutputStream;
14 import java.security.spec.X509EncodedKeySpec;
15 import java.security.spec.PKCS8EncodedKeySpec;
16 import java.security.spec.EncodedKeySpec;
17 import java.io.FileInputStream;
18 import java.security.KeyFactory;
19
20 public class keypair{
21 public static final String X509 = "X.509";
22 public static final String RSA = "RSA";
23 public static final String PKCS8 = "PKCS#8";
24 public static final String PKCS12 = "PKCS12";
25
26 private static Key loadKey(String filename,String format,String algorithm){
27 Key ret=null;
28
29 try{
30 FileInputStream keyfis = new FileInputStream( filename );
31 byte[] data = new byte[keyfis.available()];
32 keyfis.read(data);
33 keyfis.close();
34
35 EncodedKeySpec spec = null;
36 KeyFactory keyFactory = KeyFactory.getInstance(algorithm);
37 if(PKCS8.equals(format)){
38 spec = new PKCS8EncodedKeySpec(data);
39 ret = keyFactory.generatePrivate(spec);
40 System.out.println(String.format("Loading %s in format %s",filename , ret.getFormat() ) );
41 }
42
43 if(X509.equals(format)){
44 spec = new X509EncodedKeySpec(data);
45 ret = keyFactory.generatePublic(spec);
46 System.out.println(String.format("Loading %s in format %s",filename , ret.getFormat() ) );
47 }
48 }
49 catch(Exception ex){
50 ex.printStackTrace();
51 }
52
53 return ret;
54 }
55
56 private static void saveKey(Key key,String filename){
57 try{
58 System.out.println(String.format("Saving %s in format %s",filename , key.getFormat() ) );
59 byte[] encodedKey = key.getEncoded();
60 FileOutputStream keyfos = new FileOutputStream( filename );
61 keyfos.write(encodedKey);
62 keyfos.close();
63 }
64 catch(Exception ex){
65 ex.printStackTrace();
66 }
67 }
68
69 private static byte[] encrypt(Key key,String payload){
70 byte[] res=null;
71 try{
72 Cipher cipher = Cipher.getInstance(key.getAlgorithm());
73 cipher.init(Cipher.ENCRYPT_MODE, key);
74 ByteArrayOutputStream baos = new ByteArrayOutputStream();
75 CipherOutputStream cos = new CipherOutputStream(baos, cipher);
76 byte[] b = payload.getBytes();
77 System.out.println( b.length );
78 cos.write(b);
79 cos.flush();
80 cos.close();
81 res = baos.toByteArray();
82
83 System.out.println("Res size: "+ res.length );
84 for(int i=0;i<res.length;i++){
85 System.out.print(String.format("%02X",res[i]));
86 }
87
88 System.out.println();
89 }
90 catch(Exception ex){
91 ex.printStackTrace();
92 }
93 return res;
94 }
95
96 private static void decrypt(Key key,byte[] res){
97 try{
98 Cipher cipherDec = Cipher.getInstance(key.getAlgorithm());
99 cipherDec.init(Cipher.DECRYPT_MODE, key);
100 ByteArrayOutputStream baosdec = new ByteArrayOutputStream();
101 CipherOutputStream cosdec = new CipherOutputStream(baosdec, cipherDec);
102 System.out.println( res.length );
103 cosdec.write(res);
104 cosdec.flush();
105 cosdec.close();
106 byte[] resDec = baosdec.toByteArray();
107
108 System.out.println("Res size: "+ resDec.length );
109 for(int i=0;i<resDec.length;i++){
110 System.out.print(String.format("%s",(char)resDec[i]));
111 }
112
113 System.out.println();
114
115 }
116 catch(Exception ex){
117 ex.printStackTrace();
118 }
119 }
120
121 public static void main(String args[]){
122 KeyStore ks = null;
123 java.io.FileInputStream fis = null;
124 String pass = "12345678";
125 String alias = "test1rsa";
126
127 try {
128 ks = KeyStore.getInstance(PKCS12);
129 fis = new java.io.FileInputStream("keystore1.p12");
130 ks.load(fis, pass.toCharArray());
131 fis.close();
132 KeyStore.ProtectionParameter protParam = new KeyStore.PasswordProtection(pass.toCharArray());
133 KeyStore.Entry pkEntry = ks.getEntry(alias, protParam);
134 KeyStore.PrivateKeyEntry prvKeyEntry = ((KeyStore.PrivateKeyEntry)pkEntry);
135 PrivateKey privateKey = prvKeyEntry.getPrivateKey();
136 Certificate myCert = ks.getCertificate(alias);
137 //Certificate myCert =prvKeyEntry.getCertificate();
138 PublicKey publicKey = myCert.getPublicKey();
139
140 System.out.println("PrivKeyAlg:" + privateKey.getAlgorithm() );
141 System.out.println("PubKeyAlg:" + publicKey.getAlgorithm() );
142 //------------------
143
144 byte[] res = encrypt(privateKey,"secret");
145 decrypt(publicKey,res);
146
147 byte[] resOther = encrypt(publicKey,"otherSecret");
148 decrypt(privateKey,resOther);
149 saveKey(publicKey,"publicKey.bin");
150 saveKey(privateKey,"privateKey.bin");
151
152 loadKey("publicKey.bin", X509,RSA);
153 loadKey("privateKey.bin",PKCS8,RSA);
154 loadKey("privateKey.bin",PKCS8,RSA);
155 }
156 catch(Exception ex){
157 ex.printStackTrace();
158 }
159 }
160 }
GCJ example desktop app
javac ToolbarFrame1.java BasicWindowMonitor.java # compile
java ToolbarFrame1 # run
ToolbarFrame1.java
1 /*
2 gcj --main=ToolbarFrame1 -g -o ToolbarFrame1 ToolbarFrame1.java BasicWindowMonitor.java
3 */
4 import java.awt.*;
5 import java.awt.event.*;
6
7 public class ToolbarFrame1 extends Frame implements ActionListener {
8 Button cutButton, copyButton, pasteButton;
9
10 public ToolbarFrame1() {
11 super("Toolbar Example (AWT)");
12 setSize(450, 250);
13 //addWindowListener(new BasicWindowMonitor());
14 WindowListener wl = new WindowListener(){
15 public void windowActivated(WindowEvent e){
16 System.out.println("Activated");
17 }
18
19 public void windowClosed(WindowEvent e){
20 System.out.println("Closed");
21 System.exit(0);
22 }
23
24 public void windowClosing(WindowEvent e){
25 Window w = e.getWindow();
26 w.setVisible(false);
27 w.dispose();
28 System.out.println("Closing");
29 }
30
31 public void windowDeactivated(WindowEvent e){
32 System.out.println("Deactivated");
33 }
34
35 public void windowDeiconified(WindowEvent e){
36 System.out.println("Deiconified");
37 }
38
39 public void windowIconified(WindowEvent e){
40 System.out.println("Iconified");
41 }
42
43 public void windowOpened(WindowEvent e){
44 System.out.println("Opened");
45 }
46
47 };
48 addWindowListener( wl );
49
50 Panel toolbar = new Panel();
51 toolbar.setLayout(new FlowLayout(FlowLayout.LEFT));
52
53 cutButton = new Button("Cut");
54 cutButton.addActionListener(this);
55 toolbar.add(cutButton);
56
57 copyButton = new Button("Copy");
58 copyButton.addActionListener(this);
59 toolbar.add(copyButton);
60
61 pasteButton = new Button("Paste");
62 pasteButton.addActionListener(this);
63 toolbar.add(pasteButton);
64
65 add(toolbar, BorderLayout.NORTH);
66 }
67
68 public void actionPerformed(ActionEvent ae) {
69 System.out.println(ae.getActionCommand());
70 }
71
72 public static void main(String args[]) {
73 ToolbarFrame1 tf1 = new ToolbarFrame1();
74 tf1.setVisible(true);
75 }
76
77 }
BasicWindowMonitor.java
Install in Slackware 64
Get from http://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html Linux64 tar gz
- mkdir -p /opt/java
- cp jdk-8u162-linux-x64.tar.gz /opt/java/
- cd /opt/java/
- tar xvzf jdk-8u162-linux-x64.tar.gz
- cd jdk1.8.0_162/bin
- ./java
Add to .bashrc
- ~/.bashrc
1 PATH=$PATH:/opt/java/jdk1.8.0_162/bin
Float error
https://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html What Every Computer Scientist Should Know About Floating-Point Arithmetic IEEE 754 The IEEE standard defines four different precisions: single, double, single-extended, and double-extended. Since rounding error is inherent in floating-point computation, it is important to have a way to measure this error.
Generics
Generics enable types (classes and interfaces) to be parameters when defining classes, interfaces and methods.
Advantages:
- Stronger type checks at compile time
- Elimination of casts
- Enabling programmers to implement generic algorithms
Swing test
1 /*
2 javac SwingTest.java
3 java SwingTest
4 */
5 import javax.swing.*;
6 import java.awt.event.*;
7
8 public class SwingTest {
9 private static void createFrame() {
10 JFrame frame = new JFrame("JFrameTitle");
11 frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
12 frame.setLayout(null);
13
14 JTextField jtf = new JTextField();
15 jtf.setBounds(5,80,100,25);
16
17 JLabel label = new JLabel("JLabel");
18 label.setBounds(5,5,100,25);
19 JButton button = new JButton("Press me");
20 button.setBounds(5,35,100,25);
21 ActionListener al = new ActionListener(){
22 public void actionPerformed(ActionEvent e){
23 System.out.println("Pressed " + jtf.getText() );
24 }
25 };
26 button.addActionListener( al );
27
28 frame.getContentPane().add(label);
29 frame.getContentPane().add(button);
30 frame.getContentPane().add(jtf);
31 frame.pack();
32 frame.setVisible(true);
33 frame.setSize(640,480);
34 }
35
36 public static void main(String[] args) {
37 createFrame();
38 }
39 }