public class multi {
public static void main(String args[])
{
int arr[][]= new int[2][];
arr[0]= new int[1];
arr[0]= new int[2];
int a,b,c=5;
for(a=0;a<2;a++)
{
for(b=0;b<a+1;b++)
{
arr[a][b]=c;
c++;
}
}
for(a=0;a<2;a++)
{
for(b=0;b<=a;b++)
{
System.out.println(arr[a][b]);
}
}
}
}
ERROR: Exception in thread "main" java.lang.NullPointerException
at multi.main(multi.java:14)
I do not understand what's my mistake and why this error is showing up. I am a beginner and have just started learning java. Thanks in advance
You should change:
arr[0]= new int[1];
arr[0]= new int[2];
to
arr[0]= new int[1];
arr[1]= new int[2];
Related
I have code to test as follows:
#BeforeEach
static void setup() throws IOException {
Context context = new MockLambdaContext();
mockAmazonS3Client();
}
#Test
#DisplayName("Testing handleRequest returns complete when middle base64 piece")
public void handleRequestTestMiddlePiece() throws IOException {
ApplicationHandler applicationHandler = new ApplicationHandler();
mockAmazonS3Client();
input.replace("tag","middle");
assertEquals("complete", applicationHandler.handleRequest(input, context));
}
public static void mockAmazonS3Client() throws IOException {
AmazonS3Client mockAmazonS3Client = mock(AmazonS3Client.class);
S3Object s3Object = mock(S3Object.class);
S3ObjectInputStream s3ObjectInputStream = mock(S3ObjectInputStream.class);
InputStream testInputStream = new ByteArrayInputStream("Test".getBytes());
when(mockAmazonS3Client.getObject(any(String.class), any(String.class))).thenAnswer(invocationOnMock -> {
return s3Object;
});
when(s3ObjectInputStream.read(any(byte[].class))).thenAnswer(invocation -> {
return testInputStream.read(invocation.getArgument(0));
});
when(s3Object.getObjectContent()).thenReturn(s3ObjectInputStream);
new MockUp<AmazonS3Client>() {
#Mock
public S3Object getObject(String bucketName, String key) throws SdkClientException, AmazonServiceException {
return s3Object;
}
};
new MockUp<AmazonS3Client>() {
#Mock
PutObjectResult putObject(PutObjectRequest var1) throws SdkClientException, AmazonServiceException {
return null;
}
};
new MockUp<AmazonS3Client>() {
#Mock
public S3ObjectInputStream getObjectContent() {
return s3ObjectInputStream;
}
};
}
In the mockAmazonS3Client I have mocked the S3Object and the S3ObjectStream that getObject produces using mockito. I have managed to use a 'when' to have getObjectContent call an S3ObjectStream. However, when I use another 'when' to mock what happens if the S3ObjectSteam is read it throws an exception where 0 bytes are returned:
java.io.IOException: Underlying input stream returned zero bytes
It could be the second 'when' that is failing for some reason, though I'm not sure. Any thoughts will be gratefully received. Thanks.
Adapting this the following code takes a class and function name, a string of Java code, compiles the code and runs the function.
public class Compile {
static void compileAndRun(final String className, final String methodName, final String code) {
JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
DiagnosticCollector<JavaFileObject> diagnostics = new DiagnosticCollector<>();
JavaFileObject file = new JavaSourceFromString(className, code);
Iterable<? extends JavaFileObject> compilationUnits = Arrays.asList(file);
JavaCompiler.CompilationTask task = compiler.getTask(null, null, diagnostics, null, null, compilationUnits);
boolean success = task.call();
for (Diagnostic diagnostic : diagnostics.getDiagnostics()) {
System.out.println(diagnostic.getCode());
System.out.println(diagnostic.getKind());
System.out.println(diagnostic.getPosition());
System.out.println(diagnostic.getStartPosition());
System.out.println(diagnostic.getEndPosition());
System.out.println(diagnostic.getSource());
System.out.println(diagnostic.getMessage(null));
}
System.out.println("Success: " + success);
if (success) {
try {
URLClassLoader classLoader = URLClassLoader.newInstance(new URL[] { new File("").toURI().toURL() });
Class.forName("HelloWorld", true, classLoader).getDeclaredMethod(methodName, new Class[] { String[].class }).invoke(null, new Object[] { null });
} catch (ClassNotFoundException e) {
System.err.println("Class not found: " + e);
} catch (NoSuchMethodException e) {
System.err.println("No such method: " + e);
} catch (IllegalAccessException e) {
System.err.println("Illegal access: " + e);
} catch (InvocationTargetException e) {
System.err.println("Invocation target: " + e);
} catch (MalformedURLException e) {
e.printStackTrace();
}
}
}
}
class JavaSourceFromString extends SimpleJavaFileObject {
final String code;
JavaSourceFromString(String name, String code) {
super(URI.create("string:///" + name.replace('.','/') + Kind.SOURCE.extension),Kind.SOURCE);
this.code = code;
}
#Override
public CharSequence getCharContent(boolean ignoreEncodingErrors) {
return code;
}
}
You might call this using:
StringWriter writer = new StringWriter();
PrintWriter out = new PrintWriter(writer);
out.println("public class HelloWorld {");
out.println(" public static void main(String args[]) {");
out.println(" System.out.println(\"Hello World !\");");
out.println(" }");
out.println("}");
out.close();
Compile.compileAndRun("HelloWorld", "main", writer.toString());
Is it possible from inside the compiled program to call external functions and variables? e.g.
class SomeClass {
int x = 123;
void myFunc() {
StringWriter writer = new StringWriter();
PrintWriter out = new PrintWriter(writer);
out.println("public class HelloWorld {");
out.println(" public static void main(String args[]) {");
out.println(" y = foo(x);");
out.println(" }");
out.println("}");
out.close();
Compile.compileAndRun("HelloWorld", "main", writer.toString());
}
void foo(int x) {
}
}
or maybe with the foo and x in another class? Obviously I tried this, but it fails to compile. Is there a way to achieve this?
In the end I was able to use Groovy, which is a superset of the Java language, to achieve my goal, so you can write a script in Java or Groovy. Passing in variables and classes, which can of course contain variables and functions, was straight-forward, e.g.
class MyClass {
int x = 100;
void myFunc(int r) {
System.out.println("value from inside script = " + r + " !");
}
}
void groovy() {
MyClass q = new MyClass();
StringWriter writer = new StringWriter();
PrintWriter out = new PrintWriter(writer);
out.println(" System.out.println(\"Hello world\" + q.x);");
out.println(" q.x += 100;");
out.println(" q.myFunc(123)");
out.close();
// call groovy expressions from Java code
Binding binding = new Binding();
binding.setVariable("q", q);
GroovyShell shell = new GroovyShell(binding);
Object value = shell.evaluate(writer.toString());
System.out.println("new value = " + q.x);
}
Hi I am trying to create a simple sequencefile with mahout libraries using the bellow code. While running the code I am getting NullPointerException after creating a empty file,
public class SequenceFileWriter {
public static void main(String[] args) throws IOException {
Configuration conf = new Configuration();
FileSystem fs = FileSystem.get(conf);
SequenceFile.Writer sfw = new SequenceFile.Writer(fs, conf, new Path("/tmp/test.txt"), Text.class, Text.class);
Text A = new Text();
Text B = new Text();
for (int x = 0; x < 1000; x++) {
A.set("a" + x);
B.set("b" + x);
sfw.append(A, B);
}
org.apache.hadoop.io.IOUtils.closeStream(sfw);
}
}
Error:
Exception in thread "main" java.lang.NullPointerException
at java.lang.ProcessBuilder.start(ProcessBuilder.java:1010)
at org.apache.hadoop.util.Shell.runCommand(Shell.java:445)
at org.apache.hadoop.util.Shell.run(Shell.java:418)
at org.apache.hadoop.util.Shell$ShellCommandExecutor.execute(Shell.java:650)
at org.apache.hadoop.util.Shell.execCommand(Shell.java:739)
at org.apache.hadoop.util.Shell.execCommand(Shell.java:722)
at org.apache.hadoop.fs.RawLocalFileSystem.setPermission(RawLocalFileSystem.java:633)
at org.apache.hadoop.fs.FilterFileSystem.setPermission(FilterFileSystem.java:467)
at org.apache.hadoop.fs.ChecksumFileSystem.create(ChecksumFileSystem.java:456)
at org.apache.hadoop.fs.ChecksumFileSystem.create(ChecksumFileSystem.java:424)
at org.apache.hadoop.fs.FileSystem.create(FileSystem.java:906)
at org.apache.hadoop.fs.FileSystem.create(FileSystem.java:887)
at org.apache.hadoop.fs.FileSystem.create(FileSystem.java:784)
at org.apache.hadoop.fs.FileSystem.create(FileSystem.java:773)
at org.apache.hadoop.io.SequenceFile$Writer.<init>(SequenceFile.java:1103)
at com.jarvis.trial.SequenceFileWriter.main(SequenceFileWriter.java:15)
Could anyone please help me on this to sort the issue?
I am trying to connect localhost and insert data into database through j2me application.but when I am connecting the server it shows there is a nullpointerexception 0 error.
this is midlet code
import java.io.DataOutputStream;
import java.io.InputStream;
import javax.microedition.io.HttpConnection;
import javax.microedition.lcdui.Command;
import javax.microedition.lcdui.CommandListener;
import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Displayable;
import javax.microedition.lcdui.Form;
import javax.microedition.lcdui.StringItem;
import javax.microedition.midlet.*;
public class Midlet_1 extends MIDlet implements CommandListener {
Display mdDisplay;
Form mForm;
StringItem messageitem;
Command exit, connectCommand;
public Midlet_1() {
mForm = new Form("My Counter midlet");
messageitem = new StringItem(null, "");
exit = new Command("Exit", Command.EXIT, 0);
connectCommand = new Command("Connect", Command.SCREEN, 0);
mForm.append(messageitem);
mForm.addCommand(exit);
mForm.addCommand(connectCommand);
mForm.setCommandListener(this);
}
public void startApp() {
mdDisplay = Display.getDisplay(this);
mdDisplay.setCurrent(mForm);
}
public void pauseApp() {
}
public void destroyApp(boolean unconditional) {
}
public void commandAction(Command c, Displayable d) {
if (c == exit) {
notifyDestroyed();
} else if (c == connectCommand) {
Form waitform = new Form("Waiting");
mdDisplay.setCurrent(waitform);
Thread t = new Thread() {
public void run() {
connect();
}
};
t.start();
}
}
private void connect() {
try {
HttpConnection hs = null;
InputStream in = null;
String url = "localhost:8080/testweb/src/save";
hs.setRequestProperty("User-Agent", "Profile/MIDP-2.0,Configuration/CLDC-2.0");
hs.setRequestProperty("Content-Language", "en-US");
hs.setRequestMethod(HttpConnection.POST);
DataOutputStream ds = hs.openDataOutputStream();
ds.writeUTF("nam56");
ds.writeUTF("67");
ds.writeUTF("0716522549");
ds.flush();
ds.close();
in = hs.openInputStream();
int connectlength = (int) hs.getLength();
byte[] raw = new byte[connectlength];
int length = in.read(raw);
// int ch;
// StringBuffer sb=new StringBuffer();
// while((ch=in.read())!=-1){
// sb.append((char)ch);
// }
in.close();
hs.close();
String s = new String(raw, 0, length);
messageitem.setText(s);
} catch (Exception e) {
messageitem.setText(e.toString());
System.out.println(e);
}
mdDisplay.setCurrent(mForm);
}
}
and this is servlet code
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException, ClassNotFoundException, SQLException {
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
try {
DataInputStream in=new DataInputStream(request.getInputStream());
String name=in.readUTF();
String id=in.readUTF();
String contt=in.readUTF();
Connection c=DBcon.setconConnection();
Statement s=c.createStatement();
s.executeUpdate("insert into details values('"+id+"','"+name+"''"+contt+"')");
out.print("successfullllll");
} finally {
out.close();
}
}
please check this out.....
This might work only if you are running an emulator on the same machine as the server. Try to replace locahost by 127.0.0.1.
In your connect() method, I can see that you initialized hs as null then you called setRequestProperty. Try to initialize hs properly before calling its methods.
JPanel p2 = new JPanel(new GridLayout(6,1));
ButtonGroup tubtype = new ButtonGroup();
JRadioButton roundrButton = new JRadioButton("Round", true);
tubtype.add(roundrButton);
JRadioButton ovalrButton = new JRadioButton("Oval", false);
tubtype.add(ovalrButton);
calcButton = new JButton("Calculate Volume");
exitButton = new JButton("Exit");
hlength = new JTextField(5);
hwidth = new JTextField(5);
hdepth = new JTextField(5);
hvolume = new JTextField(5);
lengthLabel = new JLabel("Enter the tub's length (ft):");
widthLabel = new JLabel("Enter the tub's width (ft):");
depthLabel = new JLabel("Enter the tub's depth (ft):");
volumeLabel = new JLabel("The tub's volume (ft^3):");
p2.add(roundrButton);
p2.add(ovalrButton);
p2.add(lengthLabel);
p2.add(hlength);
p2.add(widthLabel);
p2.add(hwidth);
p2.add(depthLabel);
p2.add(hdepth);
p2.add(volumeLabel);
p2.add(hvolume);
p2.add(calcButton);
p2.add(exitButton);
tab.addTab( "Hot Tubs", null, p2, " Panel #1" );
calcButtonHandler2 ihandler =new calcButtonHandler2();
calcButton.addActionListener(ihandler);
exitButtonHandler ghandler =new exitButtonHandler();
exitButton.addActionListener(ghandler);
FocusHandler hhandler =new FocusHandler();
hlength.addFocusListener(hhandler);
hwidth.addFocusListener(hhandler);
hdepth.addFocusListener(hhandler);
hvolume.addFocusListener(hhandler);
// add JTabbedPane to container
getContentPane().add( tab );
setSize( 550, 500 );
setVisible( true );
}
public class calcButtonHandler implements ActionListener {
public void actionPerformed(ActionEvent e) {
DecimalFormat num =new DecimalFormat(",###.##");
double sLength, sWidth, sdepth, Total;
sLength = Double.valueOf(plength.getText());
sWidth =Double.valueOf(pwidth.getText());
sdepth =Double.valueOf(pdepth.getText());
if(e.getSource() == pcalcButton) {
Total = sLength * sWidth * sdepth;
pvolume.setText(num.format(Total));
try{
String value=pvolume.getText();
File file = new File("output.txt");
FileWriter fstream = new FileWriter(file,true);
BufferedWriter out = new BufferedWriter(fstream);
out.write("Length= "+sLength+", Width= "+sWidth+", Depth= "+sdepth+" so the volume of Swimming Pool is "+value);
out.newLine();
out.close();
}
catch(Exception ex){}
}
}
}
public class calcButtonHandler2 implements ActionListener {
public void actionPerformed(ActionEvent g) {
DecimalFormat num =new DecimalFormat(",###.##");
double cLength, cWidth, cdepth, Total;
cLength = Double.valueOf(hlength.getText());
cWidth = Double.valueOf(hwidth.getText());
cdepth = Double.valueOf(hdepth.getText());
try
{
AbstractButton roundrButton;
if(roundrButton.isSelected())
{
Total = Math.PI * Math.pow(cLength / 2.0, 2) * cdepth;
}
else
{
Total = Math.PI * Math.pow(cLength * cWidth, 2) * cdepth;
}
hvolume.setText(""+num.format(Total));
}
catch(Exception ex){}
}
}
}
class exitButtonHandler implements ActionListener {
public void actionPerformed(ActionEvent g){
System.exit(0);
}
}
class FocusHandler implements FocusListener {
public void focusGained(FocusEvent e) {
}
public void focusLost(FocusEvent e) {
}
public static void main( String args[] )
{
Final tabs = new Final();
tabs.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
}
I am getting an error that says my roundrButton may not have been initialized. Please help.
The problem is these lines here:
try
{
AbstractButton roundrButton;
if(roundrButton.isSelected())
{
You're declaring a variable called roundrButton, and then attempting to call .isSelected() on it. You never assign anything to roundButton, though, so it is going to be null.
It seems like you might want to be referring to the roundrButton that you declared earlier. Have you considered making it a field of your class?
The error happens here:
try {
AbstractButton roundrButton;
if (roundrButton.isSelected()) {
You declared a variable called roundrButton but did not assign any object to it.
Then you called a method on, well, who knows? There is no object on which to call the method, because the variable roundrButton never received a value.
I guess your problem is in method actionPerformed of class calcButtonHandler2 :
try {
AbstractButton roundrButton;
if(roundrButton.isSelected())
roundrButton is indeed not initialized and it will lead to a NullPointerException at runtime.