It's the first time I'm doing this so I didn't want to be lengthy. I'm building a cross reference from reading a java program. I'm to exclude java keywords, commented words and words in quotations. I got through with excluding the java keywords and the commented words but I'm having problems excluding those in quotes.
public class CrossReference {
static Scanner in;
static PrintWriter out;
static int currentLine = 0;
public static void main(String[] args) throws IOException {
in = new Scanner (new FileReader("keywords.txt"));
out = new PrintWriter (new FileWriter("crossreference.out"));
LinkedList keywords = new LinkedList();
while (in.hasNextLine()) {
String word = in.nextLine();
keywords.addTail(new NodeData(word));
}
in = new Scanner (new FileReader("program.txt"));
BinaryTree bst = new BinaryTree();
while(in.hasNextLine()){
String line = in.nextLine();
out.printf("%3d. %s\n", ++currentLine,line);
getWordsOnLine(line,bst,keywords);
}
out.printf("\nWords LineNumber\n\n");
bst.inOrder();
out.close();
}
public static void getWordsOnLine(String inputLine, BinaryTree bst, LinkedList keywords){
Scanner inLine = new Scanner(inputLine);
inLine.useDelimiter("[^a-zA-Z//\"*]+");
boolean b = true;
while(inLine.hasNext() && b){
String word = inLine.next().toLowerCase();
if (word.contains("/") || word.contains("\"") || word.contains("*")) {
b = false;
} //this works for the commented words but not so well for the ones in quotes as it also excludes words after those in quotes
else {
boolean key = false;
Node curr = keywords.head;
while (curr != null) {
if (curr.data.str.equals(word)) key = true;
curr = curr.next;
}
if (key == false) {
TreeNode node = bst.findOrInsert(new TreeNodeData(word));
ListNode p = new ListNode(currentLine);
p.next = node.data.firstLine;
node.data.firstLine = p;
}
}
}
}
}
Split your string by space into an array.
Iterate through the array, checking which elements start with quotes and are words
Sum it
So the code would look like:
public class HelloWorld
{
public static void main(String[] args)
{
String a = "COPY PASTE ORIGINAL HERE";
String[] arr = a.split(" ");
int count = 0;
for(String each: arr){
if(each.charAt(0) != '\"' && each.charAt(0) < '0' || each.charAt(0) > '9'){
count++;
}
}
System.out.println("words="+count);
}
}
Related
Are there any Dart resources that would split a command-line String into a List<String> of arguments?
ArgsParser takes a List<String> of already split arguments usually from main(List<String>).
To answer my own question,
I've converted a Java function I liked into a Dart Converter<String, List<String>) class:
import 'dart:convert';
/// Splits a `String` into a list of command-line argument parts.
/// e.g. "command -p param" -> ["command", "-p", "param"]
///
class CommandlineConverter extends Converter<String, List<String>>
{
#override
List<String> convert(String input)
{
if (input == null || input.isEmpty)
{
//no command? no string
return [];
}
final List<String> result = new List<String>();
var current = "";
String inQuote;
bool lastTokenHasBeenQuoted = false;
for (int index = 0; index < input.length; index++)
{
final token = input[index];
if (inQuote != null)
{
if (token == inQuote)
{
lastTokenHasBeenQuoted = true;
inQuote = null;
}
else
{
current += token;
}
}
else
{
switch (token)
{
case "'": // '
case '"': // ""
inQuote = token;
continue;
case " ": // space
if (lastTokenHasBeenQuoted || current.isNotEmpty)
{
result.add(current);
current = "";
}
break;
default:
current += token;
lastTokenHasBeenQuoted = false;
}
}
}
if (lastTokenHasBeenQuoted || current.isNotEmpty)
{
result.add(current);
}
if (inQuote != null)
{
throw new Exception("Unbalanced quote $inQuote in input:\n$input");
}
return result;
}
}
Is it possible to change the record delimiter from newline to some other string so as to read a file with newlines into a single tuple in pig.
Yes.
A = LOAD '...' USING PigStorage(',') AS (...); //comma is the delimeter for fields
SET textinputformat.record.delimiter '<delimeter>'; // record delimeter, by default it is `\n`. You can change to any delimeter.
As mentioned here
You can use PigStorage
A = LOAD '/some/path/COMMA-DELIM-PREFIX*' USING PigStorage(',') AS (f1:chararray, ...);
B = LOAD '/some/path/SEMICOLON-DELIM-PREFIX*' USING PigStorage('\t') AS (f1:chararray, ...);
You can even try writing load/store UDF.
There is java code example for both load and store.
Load Functions : LoadFunc abstract class has the main methods for loading data and for most use cases it would suffice to extend it. You can read more here
Example
The loader implementation in the example is a loader for text data
with line delimiter as '\n' and '\t' as default field delimiter (which
can be overridden by passing a different field delimiter in the
constructor) - this is similar to current PigStorage loader in Pig.
The implementation uses an existing Hadoop supported Inputformat -
TextInputFormat - as the underlying InputFormat.
public class SimpleTextLoader extends LoadFunc {
protected RecordReader in = null;
private byte fieldDel = '\t';
private ArrayList<Object> mProtoTuple = null;
private TupleFactory mTupleFactory = TupleFactory.getInstance();
private static final int BUFFER_SIZE = 1024;
public SimpleTextLoader() {
}
/**
* Constructs a Pig loader that uses specified character as a field delimiter.
*
* #param delimiter
* the single byte character that is used to separate fields.
* ("\t" is the default.)
*/
public SimpleTextLoader(String delimiter) {
this();
if (delimiter.length() == 1) {
this.fieldDel = (byte)delimiter.charAt(0);
} else if (delimiter.length() > 1 & & delimiter.charAt(0) == '\\') {
switch (delimiter.charAt(1)) {
case 't':
this.fieldDel = (byte)'\t';
break;
case 'x':
fieldDel =
Integer.valueOf(delimiter.substring(2), 16).byteValue();
break;
case 'u':
this.fieldDel =
Integer.valueOf(delimiter.substring(2)).byteValue();
break;
default:
throw new RuntimeException("Unknown delimiter " + delimiter);
}
} else {
throw new RuntimeException("PigStorage delimeter must be a single character");
}
}
#Override
public Tuple getNext() throws IOException {
try {
boolean notDone = in.nextKeyValue();
if (!notDone) {
return null;
}
Text value = (Text) in.getCurrentValue();
byte[] buf = value.getBytes();
int len = value.getLength();
int start = 0;
for (int i = 0; i < len; i++) {
if (buf[i] == fieldDel) {
readField(buf, start, i);
start = i + 1;
}
}
// pick up the last field
readField(buf, start, len);
Tuple t = mTupleFactory.newTupleNoCopy(mProtoTuple);
mProtoTuple = null;
return t;
} catch (InterruptedException e) {
int errCode = 6018;
String errMsg = "Error while reading input";
throw new ExecException(errMsg, errCode,
PigException.REMOTE_ENVIRONMENT, e);
}
}
private void readField(byte[] buf, int start, int end) {
if (mProtoTuple == null) {
mProtoTuple = new ArrayList<Object>();
}
if (start == end) {
// NULL value
mProtoTuple.add(null);
} else {
mProtoTuple.add(new DataByteArray(buf, start, end));
}
}
#Override
public InputFormat getInputFormat() {
return new TextInputFormat();
}
#Override
public void prepareToRead(RecordReader reader, PigSplit split) {
in = reader;
}
#Override
public void setLocation(String location, Job job)
throws IOException {
FileInputFormat.setInputPaths(job, location);
}
}
Store Functions : StoreFunc abstract class has the main methods for storing data and for most use cases it should suffice to extend it
Example
The storer implementation in the example is a storer for text data
with line delimiter as '\n' and '\t' as default field delimiter (which
can be overridden by passing a different field delimiter in the
constructor) - this is similar to current PigStorage storer in Pig.
The implementation uses an existing Hadoop supported OutputFormat -
TextOutputFormat as the underlying OutputFormat.
public class SimpleTextStorer extends StoreFunc {
protected RecordWriter writer = null;
private byte fieldDel = '\t';
private static final int BUFFER_SIZE = 1024;
private static final String UTF8 = "UTF-8";
public PigStorage() {
}
public PigStorage(String delimiter) {
this();
if (delimiter.length() == 1) {
this.fieldDel = (byte)delimiter.charAt(0);
} else if (delimiter.length() > 1delimiter.charAt(0) == '\\') {
switch (delimiter.charAt(1)) {
case 't':
this.fieldDel = (byte)'\t';
break;
case 'x':
fieldDel =
Integer.valueOf(delimiter.substring(2), 16).byteValue();
break;
case 'u':
this.fieldDel =
Integer.valueOf(delimiter.substring(2)).byteValue();
break;
default:
throw new RuntimeException("Unknown delimiter " + delimiter);
}
} else {
throw new RuntimeException("PigStorage delimeter must be a single character");
}
}
ByteArrayOutputStream mOut = new ByteArrayOutputStream(BUFFER_SIZE);
#Override
public void putNext(Tuple f) throws IOException {
int sz = f.size();
for (int i = 0; i < sz; i++) {
Object field;
try {
field = f.get(i);
} catch (ExecException ee) {
throw ee;
}
putField(field);
if (i != sz - 1) {
mOut.write(fieldDel);
}
}
Text text = new Text(mOut.toByteArray());
try {
writer.write(null, text);
mOut.reset();
} catch (InterruptedException e) {
throw new IOException(e);
}
}
#SuppressWarnings("unchecked")
private void putField(Object field) throws IOException {
//string constants for each delimiter
String tupleBeginDelim = "(";
String tupleEndDelim = ")";
String bagBeginDelim = "{";
String bagEndDelim = "}";
String mapBeginDelim = "[";
String mapEndDelim = "]";
String fieldDelim = ",";
String mapKeyValueDelim = "#";
switch (DataType.findType(field)) {
case DataType.NULL:
break; // just leave it empty
case DataType.BOOLEAN:
mOut.write(((Boolean)field).toString().getBytes());
break;
case DataType.INTEGER:
mOut.write(((Integer)field).toString().getBytes());
break;
case DataType.LONG:
mOut.write(((Long)field).toString().getBytes());
break;
case DataType.FLOAT:
mOut.write(((Float)field).toString().getBytes());
break;
case DataType.DOUBLE:
mOut.write(((Double)field).toString().getBytes());
break;
case DataType.BYTEARRAY: {
byte[] b = ((DataByteArray)field).get();
mOut.write(b, 0, b.length);
break;
}
case DataType.CHARARRAY:
// oddly enough, writeBytes writes a string
mOut.write(((String)field).getBytes(UTF8));
break;
case DataType.MAP:
boolean mapHasNext = false;
Map<String, Object> m = (Map<String, Object>)field;
mOut.write(mapBeginDelim.getBytes(UTF8));
for(Map.Entry<String, Object> e: m.entrySet()) {
if(mapHasNext) {
mOut.write(fieldDelim.getBytes(UTF8));
} else {
mapHasNext = true;
}
putField(e.getKey());
mOut.write(mapKeyValueDelim.getBytes(UTF8));
putField(e.getValue());
}
mOut.write(mapEndDelim.getBytes(UTF8));
break;
case DataType.TUPLE:
boolean tupleHasNext = false;
Tuple t = (Tuple)field;
mOut.write(tupleBeginDelim.getBytes(UTF8));
for(int i = 0; i < t.size(); ++i) {
if(tupleHasNext) {
mOut.write(fieldDelim.getBytes(UTF8));
} else {
tupleHasNext = true;
}
try {
putField(t.get(i));
} catch (ExecException ee) {
throw ee;
}
}
mOut.write(tupleEndDelim.getBytes(UTF8));
break;
case DataType.BAG:
boolean bagHasNext = false;
mOut.write(bagBeginDelim.getBytes(UTF8));
Iterator<Tuple> tupleIter = ((DataBag)field).iterator();
while(tupleIter.hasNext()) {
if(bagHasNext) {
mOut.write(fieldDelim.getBytes(UTF8));
} else {
bagHasNext = true;
}
putField((Object)tupleIter.next());
}
mOut.write(bagEndDelim.getBytes(UTF8));
break;
default: {
int errCode = 2108;
String msg = "Could not determine data type of field: " + field;
throw new ExecException(msg, errCode, PigException.BUG);
}
}
}
#Override
public OutputFormat getOutputFormat() {
return new TextOutputFormat<WritableComparable, Text>();
}
#Override
public void prepareToWrite(RecordWriter writer) {
this.writer = writer;
}
#Override
public void setStoreLocation(String location, Job job) throws IOException {
job.getConfiguration().set("mapred.textoutputformat.separator", "");
FileOutputFormat.setOutputPath(job, new Path(location));
if (location.endsWith(".bz2")) {
FileOutputFormat.setCompressOutput(job, true);
FileOutputFormat.setOutputCompressorClass(job, BZip2Codec.class);
} else if (location.endsWith(".gz")) {
FileOutputFormat.setCompressOutput(job, true);
FileOutputFormat.setOutputCompressorClass(job, GzipCodec.class);
}
}
}
I am reading bunch of integers separated by space or newlines from the standard in using Scanner(System.in).
Is there any faster way of doing this in Java?
Is there any faster way of doing this in Java?
Yes. Scanner is fairly slow (at least according to my experience).
If you don't need to validate the input, I suggest you just wrap the stream in a BufferedInputStream and use something like String.split / Integer.parseInt.
A small comparison:
Reading 17 megabytes (4233600 numbers) using this code
Scanner scanner = new Scanner(System.in);
while (scanner.hasNext())
sum += scanner.nextInt();
took on my machine 3.3 seconds. while this snippet
BufferedReader bi = new BufferedReader(new InputStreamReader(System.in));
String line;
while ((line = bi.readLine()) != null)
for (String numStr: line.split("\\s"))
sum += Integer.parseInt(numStr);
took 0.7 seconds.
By messing up the code further (iterating over line with String.indexOf / String.substring) you can get it down to about 0.1 seconds quite easily, but I think I've answered your question and I don't want to turn this into some code golf.
I created a small InputReader class which works just like Java's Scanner but outperforms it in speed by many magnitudes, in fact, it outperforms the BufferedReader as well. Here is a bar graph which shows the performance of the InputReader class I have created reading different types of data from standard input:
Here are two different ways of finding the sum of all the numbers coming from System.in using the InputReader class:
int sum = 0;
InputReader in = new InputReader(System.in);
// Approach #1
try {
// Read all strings and then parse them to integers (this is much slower than the next method).
String strNum = null;
while( (strNum = in.nextString()) != null )
sum += Integer.parseInt(strNum);
} catch (IOException e) { }
// Approach #2
try {
// Read all the integers in the stream and stop once an IOException is thrown
while( true ) sum += in.nextInt();
} catch (IOException e) { }
If you asking from competitive programming point of view, where if the submission is not fast enough, it will be TLE.
Then you can check the following method to retrieve String from System.in.
I have taken from one of the best coder in java(competitive sites)
private String ns()
{
int b = skip();
StringBuilder sb = new StringBuilder();
while(!(isSpaceChar(b))){ // when nextLine, (isSpaceChar(b) && b != ' ')
sb.appendCodePoint(b);
b = readByte();
}
return sb.toString();
}`
You can read from System.in in a digit by digit way. Look at this answer: https://stackoverflow.com/a/2698772/3307066.
I copy the code here (barely modified). Basically, it reads integers, separated by anything that is not a digit. (Credits to the original author.)
private static int readInt() throws IOException {
int ret = 0;
boolean dig = false;
for (int c = 0; (c = System.in.read()) != -1; ) {
if (c >= '0' && c <= '9') {
dig = true;
ret = ret * 10 + c - '0';
} else if (dig) break;
}
return ret;
}
In my problem, this code was approx. 2 times faster than using StringTokenizer, which was already faster than String.split(" ").
(The problem involved reading 1 million integers of up to 1 million each.)
StringTokenizer is a much faster way of reading string input separated by tokens.
Check below example to read a string of integers separated by space and store in arraylist,
String str = input.readLine(); //read string of integers using BufferedReader e.g. "1 2 3 4"
List<Integer> list = new ArrayList<>();
StringTokenizer st = new StringTokenizer(str, " ");
while (st.hasMoreTokens()) {
list.add(Integer.parseInt(st.nextToken()));
}
In programming perspective this customized Scan and Print class is way better than Java inbuilt Scanner and BufferedReader classes.
import java.io.InputStream;
import java.util.InputMismatchException;
import java.io.IOException;
public class Scan
{
private byte[] buf = new byte[1024];
private int total;
private int index;
private InputStream in;
public Scan()
{
in = System.in;
}
public int scan() throws IOException
{
if(total < 0)
throw new InputMismatchException();
if(index >= total)
{
index = 0;
total = in.read(buf);
if(total <= 0)
return -1;
}
return buf[index++];
}
public int scanInt() throws IOException
{
int integer = 0;
int n = scan();
while(isWhiteSpace(n)) /* remove starting white spaces */
n = scan();
int neg = 1;
if(n == '-')
{
neg = -1;
n = scan();
}
while(!isWhiteSpace(n))
{
if(n >= '0' && n <= '9')
{
integer *= 10;
integer += n-'0';
n = scan();
}
else
throw new InputMismatchException();
}
return neg*integer;
}
public String scanString()throws IOException
{
StringBuilder sb = new StringBuilder();
int n = scan();
while(isWhiteSpace(n))
n = scan();
while(!isWhiteSpace(n))
{
sb.append((char)n);
n = scan();
}
return sb.toString();
}
public double scanDouble()throws IOException
{
double doub=0;
int n=scan();
while(isWhiteSpace(n))
n=scan();
int neg=1;
if(n=='-')
{
neg=-1;
n=scan();
}
while(!isWhiteSpace(n)&& n != '.')
{
if(n>='0'&&n<='9')
{
doub*=10;
doub+=n-'0';
n=scan();
}
else throw new InputMismatchException();
}
if(n=='.')
{
n=scan();
double temp=1;
while(!isWhiteSpace(n))
{
if(n>='0'&&n<='9')
{
temp/=10;
doub+=(n-'0')*temp;
n=scan();
}
else throw new InputMismatchException();
}
}
return doub*neg;
}
public boolean isWhiteSpace(int n)
{
if(n == ' ' || n == '\n' || n == '\r' || n == '\t' || n == -1)
return true;
return false;
}
public void close()throws IOException
{
in.close();
}
}
And the customized Print class can be as follows
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.OutputStreamWriter;
public class Print
{
private BufferedWriter bw;
public Print()
{
this.bw = new BufferedWriter(new OutputStreamWriter(System.out));
}
public void print(Object object)throws IOException
{
bw.append("" + object);
}
public void println(Object object)throws IOException
{
print(object);
bw.append("\n");
}
public void close()throws IOException
{
bw.close();
}
}
You can use BufferedReader for reading data
BufferedReader inp = new BufferedReader(new InputStreamReader(System.in));
int t = Integer.parseInt(inp.readLine());
while(t-->0){
int n = Integer.parseInt(inp.readLine());
int[] arr = new int[n];
String line = inp.readLine();
String[] str = line.trim().split("\\s+");
for(int i=0;i<n;i++){
arr[i] = Integer.parseInt(str[i]);
}
And for printing use StringBuffer
StringBuffer sb = new StringBuffer();
for(int i=0;i<n;i++){
sb.append(arr[i]+" ");
}
System.out.println(sb);
Here is the full version fast reader and writer. I also used Buffering.
import java.io.*;
import java.util.*;
public class FastReader {
private static StringTokenizer st;
private static BufferedReader in;
private static PrintWriter pw;
public static void main(String[] args) throws IOException {
in = new BufferedReader(new InputStreamReader(System.in));
pw = new PrintWriter(new BufferedWriter(new OutputStreamWriter(System.out)));
st = new StringTokenizer("");
pw.close();
}
private static int nextInt() throws IOException {
return Integer.parseInt(next());
}
private static long nextLong() throws IOException {
return Long.parseLong(next());
}
private static double nextDouble() throws IOException {
return Double.parseDouble(next());
}
private static String next() throws IOException {
while(!st.hasMoreElements() || st == null){
st = new StringTokenizer(in.readLine());
}
return st.nextToken();
}
}
Reading from disk, again and again, makes the Scanner slow. I like to use the combination of BufferedReader and Scanner to get the best of both worlds. i.e. speed of BufferredReader and rich and easy API of the scanner.
Scanner scanner = new Scanner(new BufferedReader(new InputStreamReader(System.in)));
I'm making a program in java that essentially knows a variety of ocean animals, asks the user to think of an animal, and then asks the user questions until it is ready to make a guess. I used a binary tree to do this. here is my code as of right now:
import java.util.Scanner;
public class TwentyQuestions
{
private static Scanner stdin = new Scanner(System.in);
public static void main(String[ ] args)
{
BTNode<String> root;
instruct( );
root = beginningTree( );
do
play(root);
while (query("Shall we play again?"));
System.out.println("Thanks for teaching me a thing or two.");
System.out.println ("Here is the tree:");
root.print(1);
}
public static void instruct( )
{
System.out.println("Please think of an ocean animal.");
System.out.println("I will ask some yes/no questions to try to figure out which animal you're thinking of.");
}
public static void play(BTNode<String> current)
{
while (!current.isLeaf( ))
{
if (query(current.getData( )))
current = current.getLeft( );
else
current = current.getRight( );
}
System.out.print("My guess is " + current.getData( ) + ". ");
if (!query("Am I right?"))
learn(current);
else
System.out.println("I knew it all along!");
}
public static BTNode<String> beginningTree( )
{
BTNode<String> root;
BTNode<String> child;
BTNode<String> child1;
BTNode<String> child2;
BTNode<String> child3;
BTNode<String> child4;
BTNode<String> child5;
BTNode<String> child6;
BTNode<String> child7;
BTNode<String> child8;
BTNode<String> child9;
BTNode<String> child10;
BTNode<String> child11;
BTNode<String> child12;
BTNode<String> child13;
BTNode<String> child14;
final String ROOT_QUESTION = "Is it a mammal?";
final String LEFT_QUESTION = "Is it able to move on land?";
final String LEFT_QUESTION2 = "Is it a solitary animal?";
final String RIGHT_QUESTION2 = "Is it larger than a truck?";
final String RIGHT_QUESTION3 = "Does it have tusks?";
final String RIGHT_QUESTION = "Does it have any limbs/tentacles?";
final String LEFT_QUESTION4 = "Does it have more than four limbs/tentacles?";
final String LEFT_QUESTION5 = "Does it have an exoskeleton?";
final String LEFT_QUESTION6 = "Does it have claws?";
final String LEFT_QUESTION7 = "Does it have a long tail?";
final String RIGHT_QUESTION7 = "Does it have 8 arms?";
final String RIGHT_QUESTION5 = "Does it have a shell?";
final String RIGHT_QUESTION4 = "Can it sting?";
final String LEFT_QUESTION8 = "Is it long and snakelike?";
final String RIGHT_QUESTION8 = "Is it generally smaller than a car?";
final String ANIMAL1 = "Seal";
final String ANIMAL2 = "Sea Lion";
final String ANIMAL3 = "Walrus";
final String ANIMAL4 = "Whale";
final String ANIMAL5 = "Dolphin";
final String ANIMAL6 = "Shrimp";
final String ANIMAL7 = "Lobster";
final String ANIMAL8 = "Crab";
final String ANIMAL9 = "Jellyfish";
final String ANIMAL10 = "Octopus";
final String ANIMAL11 = "Squid";
final String ANIMAL12 = "Turtle";
final String ANIMAL13 = "Alligator";
final String ANIMAL14 = "Eel";
final String ANIMAL15 = "Stingray";
final String ANIMAL16 = "Shark";
final String ANIMAL17 = "Fish";
// Create the root node with the question “Are you a mammal?”
root = new BTNode<String>(ROOT_QUESTION, null, null);
child = new BTNode<String>(LEFT_QUESTION, child2, child14);
root.setLeft(child);
child2 = new BTNode<String>(LEFT_QUESTION2,null,child3);
child2.setLeft(new BTNode<String>(ANIMAL1, null, null));
child.setLeft(child2);
child14 = new BTNode<String>(RIGHT_QUESTION2,null,null);
child14.setLeft(new BTNode<String>(ANIMAL4,null,null));
child14.setRight(new BTNode<String>(ANIMAL5,null,null));
child.setRight(child14);
child3 = new BTNode<String>(RIGHT_QUESTION3, null, null);
child3.setLeft(new BTNode<String>(ANIMAL3, null, null));
child3.setRight(new BTNode<String>(ANIMAL2, null, null));
child.setRight(child3);
child1 = new BTNode<String>(RIGHT_QUESTION, child4, child8);
root.setRight(child1);
child4 = new BTNode<String>(LEFT_QUESTION4,child5,child10);
child1.setLeft(child4);
child5 = new BTNode<String>(LEFT_QUESTION5,child6,child8);
child4.setLeft(child5);
child6 = new BTNode<String>(LEFT_QUESTION6,child7, null);
child6.setRight(new BTNode<String>(ANIMAL6,null,null));
child5.setLeft(child6);
child7 = new BTNode<String>(LEFT_QUESTION7, null, null);
child7.setLeft(new BTNode<String>(ANIMAL7,null,null));
child7.setRight(new BTNode<String>(ANIMAL8,null,null));
child6.setLeft(child7);
child8 = new BTNode<String>(RIGHT_QUESTION4,null,child9);
child8.setLeft(new BTNode<String>(ANIMAL9,null,null));
child5.setRight(child8);
child9 = new BTNode<String>(RIGHT_QUESTION7,null,null);
child9.setLeft(new BTNode<String>(ANIMAL10,null,null));
child9.setRight(new BTNode<String>(ANIMAL11,null,null));
child8.setRight(child9);
child10 = new BTNode<String>(RIGHT_QUESTION5,null,null);
child10.setLeft(new BTNode<String>(ANIMAL12,null,null));
child10.setRight(new BTNode<String>(ANIMAL13,null,null));
child4.setRight(child10);
child11 = new BTNode<String>(RIGHT_QUESTION4,child12,child13);
child1.setRight(child11);
child12 = new BTNode<String>(LEFT_QUESTION8,null,null);
child12.setLeft(new BTNode<String>(ANIMAL14,null,null));
child12.setRight(new BTNode<String>(ANIMAL15,null,null));
child11.setLeft(child12);
child13 = new BTNode<String>(RIGHT_QUESTION8,null,null);
child13.setLeft(new BTNode<String>(ANIMAL17,null,null));
child13.setRight(new BTNode<String>(ANIMAL16,null,null));
child11.setRight(child13);
return root;
}
public static void learn(BTNode<String> current)
{
String guessAnimal; // The animal that was just guessed
String correctAnimal; // The animal that the user was thinking of
String newQuestion; // A question to distinguish the two animals
// Set Strings for the guessed animal, correct animal and a new question.
guessAnimal = current.getData( );
System.out.println("I give up. What are you? ");
correctAnimal = stdin.nextLine( );
System.out.println("Please type a yes/no question that will distinguish a");
System.out.println(correctAnimal + " from a " + guessAnimal + ".");
newQuestion = stdin.nextLine( );
// Put the new question in the current node, and add two new children.
current.setData(newQuestion);
System.out.println("As a " + correctAnimal + ", " + newQuestion);
if (query("Please answer"))
{
current.setLeft(new BTNode<String>(correctAnimal, null, null));
current.setRight(new BTNode<String>(guessAnimal, null, null));
}
else
{
current.setLeft(new BTNode<String>(guessAnimal, null, null));
current.setRight(new BTNode<String>(correctAnimal, null, null));
}
}
public static boolean query(String prompt)
{
String answer;
System.out.print(prompt + " [Y or N]: ");
answer = stdin.nextLine( ).toUpperCase( );
while (!answer.startsWith("Y") && !answer.startsWith("N"))
{
System.out.print("Invalid response. Please type Y or N: ");
answer = stdin.nextLine( ).toUpperCase( );
}
return answer.startsWith("Y");
}
}
The error that keeps coming up is that the "variable child(+whatever number) may have not been inititalized." how do I fix this?
Oh, and here is the code for the BTNode:
public class BTNode<E>
{
private E data;
private BTNode<E> left, right;
public BTNode(E initialData, BTNode<E> initialLeft, BTNode<E> initialRight)
{
data = initialData;
left = initialLeft;
right = initialRight;
}
public E getData( )
{
return data;
}
public BTNode<E> getLeft( )
{
return left;
}
public E getLeftmostData( )
{
if (left == null)
return data;
else
return left.getLeftmostData( );
}
public BTNode<E> getRight( )
{
return right;
}
public E getRightmostData( )
{
if (left == null)
return data;
else
return left.getRightmostData( );
}
public void inorderPrint( )
{
if (left != null)
left.inorderPrint( );
System.out.println(data);
if (right != null)
right.inorderPrint( );
}
public boolean isLeaf( )
{
return (left == null) && (right == null);
}
public void preorderPrint( )
{
System.out.println(data);
if (left != null)
left.preorderPrint( );
if (right != null)
right.preorderPrint( );
}
public void postorderPrint( )
{
if (left != null)
left.postorderPrint( );
if (right != null)
right.postorderPrint( );
System.out.println(data);
}
public void print(int depth)
{
int i;
// Print the indentation and the data from the current node:
for (i = 1; i <= depth; i++)
System.out.print(" ");
System.out.println(data);
if (left != null)
left.print(depth+1);
else if (right != null)
{
for (i = 1; i <= depth+1; i++)
System.out.print(" ");
System.out.println("--");
}
if (right != null)
right.print(depth+1);
else if (left != null)
{
for (i = 1; i <= depth+1; i++)
System.out.print(" ");
System.out.println("--");
}
}
public BTNode<E> removeLeftmost( )
{
if (left == null)
return right;
else
{
left = left.removeLeftmost( );
return this;
}
}
public BTNode<E> removeRightmost( )
{
if (right == null)
return left;
else
{
right = right.removeRightmost( );
return this;
}
}
public void setData(E newData)
{
data = newData;
}
public void setLeft(BTNode<E> newLeft)
{
left = newLeft;
}
public void setRight(BTNode<E> newRight)
{
right = newRight;
}
public static <E> BTNode<E> treeCopy(BTNode<E> source)
{
BTNode<E> leftCopy, rightCopy;
if (source == null)
return null;
else
{
leftCopy = treeCopy(source.left);
rightCopy = treeCopy(source.right);
return new BTNode<E>(source.data, leftCopy, rightCopy);
}
}
public static <E> long treeSize(BTNode<E> root)
{
if (root == null)
return 0;
else
return 1 + treeSize(root.left) + treeSize(root.right);
}
}
When you declare your variables, make sure you also initialize them before using them. That is, instead of writing
BTNode<String> root;
BTNode<String> child;
BTNode<String> child1;
...
write
BTNode<String> root = null;
BTNode<String> child = null;
...
This is because when you later go on and write the statement
child = new BTNode<String>(LEFT_QUESTION, child2, child14);
child2 and child14 would have been initialized (Whereas in your case, they have only been declared, not initialized)
I'm trying to figure out how to invoke a Boolean method as true or false. Here is what I have thus far:
import java.util.Scanner;
import java.text.DecimalFormat;
public class AssignmentThree {
public static void main(String[]args) {
Scanner scan = new Scanner(System.in);
System.out.print("Enter the length of Edge 1: ");
double edge1 = scan.nextDouble();
System.out.print("Enter the length of Edge 2: ");
double edge2 = scan.nextDouble();
System.out.print("Enter the length of Edge 3: ");
double edge3 = scan.nextDouble();
scan.close();
DecimalFormat Dec = new DecimalFormat("###,###,##0.00");
if(isValid (edge1, edge2, edge3) == true) {
System.out.println("The area of the triangle is " + Dec.format(area(edge1, edge2, edge3)));
}
if(isValid (edge1, edge2, edge3) == false) {
System.out.println("This is not a valid traingle");
}
}
public static boolean isValid(double side1, double side2, double side3) {
//testing to see if the triangle is real
if(side1+side2>side3 || side1+side3>side2 || side2+side3>side1) {
return true;
} else {
return false;
}
}
I'm not sure if the problem is in my method or not but when the program is ran it simply prints the area, and never if its valid or not.