[JAVA] 1.Write a complete Java method that takes a boolean parameter, and which
ID: 666489 • Letter: #
Question
[JAVA]
1.Write a complete Java method that takes a boolean parameter, and which is declared to throw an exception of type Exception. If the value of the boolean is true, throw the exception with the message “An error occurred.” If the boolean parameter is false, do nothing.
2.Write a Java code snippet to call the method you wrote in #1 above. Make sure to handle the exception that is thrown.
3.Write a Java method that takes two parameters: an array of Strings (arrayToWrite), and a String (filename). The method writes the Strings in the array to a text file, each String on a separate line, to a file with the name passed in the fileName parameter.
4.Write a Java method that takes a String as a parameter (filename) and returns an ArrayList of Strings. The method reads the text file identified by the filename parameter and populates the ArrayList with an element for each line in the text file.
Explanation / Answer
1.Boolean methods :
Snippet :
java code with xml
package net.viralpatel.java.xmlparser;
import java.io.File;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
public class XMLParser {
public void getAllUserNames(String fileName) {
try {
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = dbf.newDocumentBuilder();
File file = new File(fileName);
if (file.exists()) {
Document doc = db.parse(file);
Element docEle = doc.getDocumentElement();
// Print root element of the document
System.out.println("Root element of the document: "
+ docEle.getNodeName());
NodeList studentList = docEle.getElementsByTagName("student");
// Print total student elements in document
System.out
.println("Total students: " + studentList.getLength());
if (studentList != null && studentList.getLength() > 0) {
for (int i = 0; i < studentList.getLength(); i++) {
Node node = studentList.item(i);
if (node.getNodeType() == Node.ELEMENT_NODE) {
System.out
.println("=====================");
Element e = (Element) node;
NodeList nodeList = e.getElementsByTagName("name");
System.out.println("Name: "
+ nodeList.item(0).getChildNodes().item(0)
.getNodeValue());
nodeList = e.getElementsByTagName("grade");
System.out.println("Grade: "
+ nodeList.item(0).getChildNodes().item(0)
.getNodeValue());
nodeList = e.getElementsByTagName("age");
System.out.println("Age: "
+ nodeList.item(0).getChildNodes().item(0)
.getNodeValue());
}
}
} else {
System.exit(1);
}
}
} catch (Exception e) {
System.out.println(e);
}
}
public static void main(String[] args) {
XMLParser parser = new XMLParser();
parser.getAllUserNames("c:\test.xml");
}
convert o zar
import java.util.zip.*;
import java.io.*;
public class ZipIt {
public static void main(String args[]) throws IOException {
if (args.length < 2) {
System.err.println("usage: java ZipIt Zip.zip file1 file2 file3");
System.exit(-1);
}
File zipFile = new File(args[0]);
if (zipFile.exists()) {
System.err.println("Zip file already exists, please try another");
System.exit(-2);
}
FileOutputStream fos = new FileOutputStream(zipFile);
ZipOutputStream zos = new ZipOutputStream(fos);
int bytesRead;
byte[] buffer = new byte[1024];
CRC32 crc = new CRC32();
for (int i=1, n=args.length; i < n; i++) {
String name = args[i];
File file = new File(name);
if (!file.exists()) {
System.err.println("Skipping: " + name);
continue;
}
BufferedInputStream bis = new BufferedInputStream(
new FileInputStream(file));
crc.reset();
while ((bytesRead = bis.read(buffer)) != -1) {
crc.update(buffer, 0, bytesRead);
}
bis.close();
// Reset to beginning of input stream
bis = new BufferedInputStream(
new FileInputStream(file));
ZipEntry entry = new ZipEntry(name);
entry.setMethod(ZipEntry.STORED);
entry.setCompressedSize(file.length());
entry.setSize(file.length());
entry.setCrc(crc.getValue());
zos.putNextEntry(entry);
while ((bytesRead = bis.read(buffer)) != -1) {
zos.write(buffer, 0, bytesRead);
}
bis.close();
}
zos.close();
}
}
}
sending email in java
import javax.mail.*;
import javax.mail.internet.*;
import java.util.*;
public void postMail( String recipients[ ], String subject, String message , String from) throws MessagingException
{
boolean debug = false;
//Set the host smtp address
Properties props = new Properties();
props.put("mail.smtp.host", "smtp.example.com");
// create some properties and get the default Session
Session session = Session.getDefaultInstance(props, null);
session.setDebug(debug);
// create a message
Message msg = new MimeMessage(session);
// set the from and to address
InternetAddress addressFrom = new InternetAddress(from);
msg.setFrom(addressFrom);
InternetAddress[] addressTo = new InternetAddress[recipients.length];
for (int i = 0; i < recipients.length; i++)
{
addressTo[i] = new InternetAddress(recipients[i]);
}
msg.setRecipients(Message.RecipientType.TO, addressTo);
// Optional : You can also set your custom headers in the Email if you Want
msg.addHeader("MyHeaderName", "myHeaderValue");
// Setting the Subject and Content Type
msg.setSubject(subject);
msg.setContent(message, "text/plain");
Transport.send(msg);
}
array strings
}
Arraylist in strings :
package com.java2novice.algos;
import java.util.Arrays;
public class MyArrayList {
private Object[] myStore;
private int actSize = 0;
public MyArrayList(){
myStore = new Object[10];
}
public Object get(int index){
if(index < actSize){
return myStore[index];
} else {
throw new ArrayIndexOutOfBoundsException();
}
}
public void add(Object obj){
if(myStore.length-actSize <= 5){
increaseListSize();
}
myStore[actSize++] = obj;
}
public Object remove(int index){
if(index < actSize){
Object obj = myStore[index];
myStore[index] = null;
int tmp = index;
while(tmp < actSize){
myStore[tmp] = myStore[tmp+1];
myStore[tmp+1] = null;
tmp++;
}
actSize--;
return obj;
} else {
throw new ArrayIndexOutOfBoundsException();
}
}
public int size(){
return actSize;
}
private void increaseListSize()
{
myStore = Arrays.copyOf(myStore, myStore.length*2);
System.out.println(" New length: "+myStore.length);
}
public static void main(String a[]){
MyArrayList mal = new MyArrayList();
mal.add(new Integer(2));
mal.add(new Integer(5));
mal.add(new Integer(1));
mal.add(new Integer(23));
mal.add(new Integer(14));
for(int i=0;i<mal.size();i++){
System.out.print(mal.get(i)+" ");
}
mal.add(new Integer(29));
System.out.println("Element at Index 5:"+mal.get(5));
System.out.println("List size: "+mal.size());
System.out.println("Removing element at index 2: "+mal.remove(2));
for(int i=0;i<mal.size();i++){
System.out.print(mal.get(i)+" ");
}
}
}
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