We Keep Coding

Limiting # of characters per line

I'm a beginner and I'm having trouble trying to display the output so that if its too big it will move it to the next line.
This is what I have so far:
import java.util.Scanner;
public class numberBracket {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.println("howMany: ");
int howMany = scanner.nextInt();
System.out.println("lineLength: ");
int lineLength = scanner.nextInt();
scanner.nextLine();
printNumbers(howMany, lineLength);
}
public static void printNumbers(int howMany, int lineLength) {
Integer charLength = Integer.valueOf(lineLength);
for(int i = 1; i <= howMany; i ++) {
String t = "[" + i + "]";
while(t.length() > charLength ) {
int index = t.lastIndexOf(' ', charLength);
System.out.print(t.substring(0, index));
t = t.substring(index + 1);
}
System.out.print(t);
}
}
}
So if they enter 10 for the lineLength it would be
[1][2][3]
[4]
and if they entered 12 it would be
[1][2][3][4]

You can use this snippet:
public static void printNumbers(int howMany, int lineLength) {
StringBuilder sb = new StringBuilder();
int length = 0;
for (int i = 1; i <= howMany; i++) {
String t = "[" + i + "]";
if (length + t.length() > lineLength) {
sb.append("\n");
length = 0;
}
length += t.length();
sb.append(t);
}
System.out.println(sb.toString());
}

public static void printNumbers(int howMany, int lineLength) {
String printed = "";
for (int i = 1; i <= howMany; i++) {
String t = "[" + i + "]";
if ((printed.length() + t.length()) > lineLength) {
printed = "";
System.out.println();
}
printed += t;
System.out.print(t);
}
}

I believe you have to check if it has room in the current line before printing.
If it does have room print it, if it doesn't, print in a new line.
public static void printNumbers(int howMany, int lineLength) {
int alreadyPrintedLength = 0;
for(int i = 1; i <= howMany; i ++) {
String t = "[" + i + "]";
int actualCharLength = t.length();
boolean hasRoomInCurrentLine = (alreadyPrintedLength + actualCharLength) <= lineLength;
if (hasRoomInCurrentLine) {
System.out.print(t);
alreadyPrintedLength += actualCharLength;
} else {
System.out.print(System.lineSeparator() + t);
alreadyPrintedLength = actualCharLength;
}
}
}

How to stop FileNotFoundException from popping up?

So I'm trying to find the two closest pairs in a text file and then find how close they are. I have most of it worked out but for some reason whenever I try to run the code the file not found exception keeps popping up. I can't seem to get it to run the actual code. Any help would be greatly appreciated.
import java.util.*;
import java.io.FileNotFoundException;
import java.io.File;
/**
*
* #author birnbook
*/
public class ClosestPair {
public static void ClosePair() { // string compare
try{
File text = new File("/Lab2%20Output.txt");
double temp = 0;
double x = 0;
double y = 0;
double stormag = 0;
// scanning the file in
Scanner scnr = new Scanner(text);
int lines = 0;
while (scnr.hasNextLine()) {
lines++;
}
Scanner scnnr = new Scanner(text);
double[] arr = new double[lines];
while (scnnr.hasNextLine()) {
String num = scnnr.nextLine();
arr[1] = Double.parseDouble(num);
}
stormag = arr[0] - arr[1];
if (stormag == 0){
stormag *= -1;
}
for(int i=0; i< arr.length;i++){
for(int k=1;k< arr.length; k++){
if(i != k){
temp = arr[i] - arr[k];
if(temp <= 0){
temp *= -1;
}
if (temp < stormag){
stormag = temp;
x = arr[i];
y = arr[k];
}
}
}
}
System.out.println("The numbers " + x + " and " + y + "are the closest pair with a difference of " + stormag);
} catch (FileNotFoundException e){
System.out.println("FileNotFoundException");
}
}
public static void main(String[] args) {
ClosePair();
}
}

What is wrong with this swapping program in Java, why and what should I do?

I am making a multiple string input random swap without using a temp variable.
But when I input, this happens a few times:
This happens more frequently... (note that the first output is always null and some outputs occasionally repeat)
My code:
import java.util.Arrays;
import java.util.Scanner;
public class myFile {
public static boolean contains(int[] array, int key) {
Arrays.sort(array);
return Arrays.binarySearch(array, key) >= 0;
}
public static void println(Object line) {
System.out.println(line);
}
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
String finalText = "";
String[] input = new String[5];
String[] swappedInput = new String[input.length];
int[] usedIndex = new int[input.length];
int swapCounter = input.length, useCounter;
for (int inputCounter = 0; inputCounter < input.length; inputCounter++) { //input
println("Enter input 1 " + (inputCounter + 1) + ": ");
input[inputCounter] = in.nextLine();
}
while (--swapCounter > 0) {
do{
useCounter = (int) Math.floor(Math.random() * input.length);
}
while (contains(usedIndex, useCounter));
swappedInput[swapCounter] = input[swapCounter].concat("#" + input[useCounter]);
swappedInput[useCounter] = swappedInput[swapCounter].split("#")[0];
swappedInput[swapCounter] = swappedInput[swapCounter].split("#")[1];
usedIndex[useCounter] = useCounter;
}
for (int outputCounter = 0; outputCounter < input.length; outputCounter++) {
finalText = finalText + swappedInput[outputCounter] + " ";
}
println("The swapped inputs are: " + finalText + ".");
}
}

Because of randomality some times useCounter is the same as swapCounter and now look at those lines (assume useCounter and swapCounter are the same)
swappedInput[swapCounter] = input[swapCounter].concat("#" + input[useCounter]);
swappedInput[useCounter] = swappedInput[swapCounter].split("#")[0];
swappedInput[swapCounter] = swappedInput[swapCounter].split("#")[1];
In the second line you are changing the value of xxx#www to be www so in the third line when doing split you dont get an array with two values you get an empty result thats why exception is thrown in addition you should not use swappedInput because it beats the pourpuse (if i understand correctly yoush shoud not use temp values while you are using addition array which is worse) the correct sollution is to only use input array here is the solution
public class myFile {
public static boolean contains(int[] array, int key) {
Arrays.sort(array);
return Arrays.binarySearch(array, key) >= 0;
}
public static void println(Object line) {
System.out.println(line);
}
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
String finalText = "";
String[] input = new String[5];
int[] usedIndex = new int[input.length];
int swapCounter = input.length, useCounter;
for (int inputCounter = 0; inputCounter < input.length; inputCounter++) { //input
println("Enter input 1 " + (inputCounter + 1) + ": ");
input[inputCounter] = in.nextLine();
}
while (--swapCounter >= 0) {
do {
useCounter = (int) Math.floor(Math.random() * input.length);
}
while (contains(usedIndex, useCounter));
// Skip if results are the same
if (useCounter == swapCounter) {
swapCounter++;
continue;
}
input[swapCounter] = input[swapCounter].concat("#" + input[useCounter]);
input[useCounter] = input[swapCounter].split("#")[0];
input[swapCounter] = input[swapCounter].split("#")[1];
usedIndex[useCounter] = useCounter;
}
for (int outputCounter = 0; outputCounter < input.length; outputCounter++) {
finalText = finalText + input[outputCounter] + " ";
}
println("The swapped inputs are: " + finalText + ".");
}
}

How Improve Run-time when sorting arrays

I have managed to create a working solution for "Mixing Milk" for USACO, but the judge says my program takes too long.
I think this has to do with the way I sort the list of Farmers by asking price in lines 29 - 44. Is there any way I can improve the run time?
/*
ID:
LANG: JAVA
TASK: milk
*/
import java.util.*;
import java.io.*;
public class milk {
public static void main(String[] args) throws IOException {
double startTime = System.currentTimeMillis();
BufferedReader s = new BufferedReader(new InputStreamReader(new FileInputStream(new File("test.in"))));
PrintWriter w = new PrintWriter(new File("test.out"));
// BufferedReader s = new BufferedReader(new InputStreamReader(new FileInputStream(new File("milk.in"))));
// PrintWriter w = new PrintWriter(new File("milk.out"));
String[] st = s.readLine().split(" ");
int N = Integer.parseInt(st[0]);
int M = Integer.parseInt(st[1]);
int[] P = new int[M];
int[] A = new int[M];
String[] sets = new String[M];
for (int i = 0; i < M; i++) {
sets[i] = s.readLine();
st = sets[i].split(" ");
P[i] = Integer.parseInt(st[0]);
}
int maxp = ("" + maxVal(P)).length();
for (int i = 0; i < M; i++) {
st = sets[i].split(" ");
while (st[0].length() < maxp) {
st[0] = "0" + st[0];
}
sets[i] = st[0] + " " + st[1];
}
Arrays.sort(sets);
int cap = 0;
for (int i = 0; i < M && cap <= N; i++) {
st = sets[i].split(" ");
P[i] = Integer.parseInt(st[0]);
A[i] = Integer.parseInt(st[1]);
cap += A[i];
}
int sum = 0;
int units = 0;
int a;
for (int i = 0; units < N; i++) {
if (A[i] <= N - units) {
sum = sum + P[i] * A[i];
units += A[i];
} else {
a = N - units;
if (a > A[i]) {
a = A[i];
}
sum = sum + P[i] * a;
units += a;
}
}
System.out.println(units);
System.out.println(sum);
w.println(sum);
w.close();
double endTime = System.currentTimeMillis();
System.out.println("Took " + ((endTime - startTime) / 1000) + " seconds.");
}
public static int maxVal(int[] x) {
int max = 0;
for (int i : x) {
if (i > max) {
max = i;
}
}
return max;
}
}
EDIT: Thanks Andreas!
Changed code and made the time limit:
/*
ID:
LANG: JAVA
TASK: milk
*/
import java.util.*;
import java.io.*;
public class milk {
public static void main(String[] args) throws IOException {
double startTime = System.currentTimeMillis();
// BufferedReader s = new BufferedReader(new InputStreamReader(new FileInputStream(new File("test.in"))));
// PrintWriter w = new PrintWriter(new File("test.out"));
BufferedReader s = new BufferedReader(new InputStreamReader(new FileInputStream(new File("milk.in"))));
PrintWriter w = new PrintWriter(new File("milk.out"));
String temp = s.readLine();
int spc = temp.indexOf(" ");
int N = Integer.parseInt(temp.substring(0, spc));
int M = Integer.parseInt(temp.substring(spc + 1));
System.out.println(N + " " + M);
int[] P = new int[M];
int[] A = new int[M];
Farmer[] f = new Farmer[M];
for (int i = 0; i < M; i++) {
temp = s.readLine();
spc = temp.indexOf(" ");
f[i] = new Farmer(Integer.parseInt(temp.substring(0, spc)), Integer.parseInt(temp.substring(spc + 1)));
}
Arrays.sort(f);
for (int i = 0; i < M; i++) {
P[i] = f[i].getPrice();
A[i] = f[i].getInventory();
}
int sum = 0;
int units = 0;
int a;
for (int i = 0; units < N; i++) {
if (A[i] <= N - units) {
sum = sum + P[i] * A[i];
units += A[i];
} else {
a = N - units;
if (a > A[i]) {
a = A[i];
}
sum = sum + P[i] * a;
units += a;
}
}
System.out.println(units);
System.out.println(sum);
w.println(sum);
w.close();
double endTime = System.currentTimeMillis();
System.out.println("Took " + ((endTime - startTime) / 1000) + " seconds.");
}
}
class Farmer implements Comparable<Farmer> {
private int price;
private int inventory;
public Farmer(int price, int inventory) {
this.price = price;
this.inventory = inventory;
}
public int getPrice() {
return price;
}
public int getInventory() {
return inventory;
}
#Override
public int compareTo(Farmer f1) {
if (f1.price != this.price) {
return this.price - f1.price;
} else if (f1.inventory != this.inventory) {
return f1.inventory - this.inventory;
} else {
return 0;
}
}
}

Java is an Object-Oriented language. Use it.
Your code keeps processing String lines, splitting and concatenating. That is slow.
Read your lines into objects containing the two integer values. Make the class implement Comparable, to sort by the two values, so you can call sort().
The processing is faster because you only parse the numbers once. The sorting is faster because you don't have to zero-pad the numbers, and you sort by integers, not string.
Since your lines consist of two integers separated by a single space, don't use split(). Use indexOf(' ') and call substring() twice. It's faster and less memory intensive.

printing optimal binary search tree in preorder dynamic programming algorith

I have just finished up computing the average cost of an OBST and I know I computed it correctly. My next task is to print the tree in preorder. I have an attempt at this using recursion but can't seem to shake the null pointer error.
Here's my code:
public class OBST {
static String[] keysA;
static Integer[][] root;
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int tot = sc.nextInt();
HashMap<String, Double> hm = new HashMap<String, Double>();
int uniqNum = 0;
String[] rawInput = new String[tot];
for(int i=0; i<tot; i++) {
String tmp1 = sc.next();
if(i==0) {
hm.put(tmp1, 1.0);
uniqNum += 1.0;
} else if( i != 0) {
if(!hm.containsKey(tmp1)) {
hm.put(tmp1, 1.0);
uniqNum += 1.0;
} else {
Double tmpfreq = 0.0;
tmpfreq = hm.get(tmp1);
hm.put(tmp1, (tmpfreq + 1.0));
}
}
}
Set<String> keys = hm.keySet();
keysA = keys.toArray(new String[uniqNum]);
Double[] freqsA = new Double[uniqNum];
Arrays.sort(keysA);
for(int i=0; i<uniqNum; i++) {
Double tmp = 0.0;
String tmpK = keysA[i];
tmp = hm.get(tmpK);
tmp = tmp/tot;
freqsA[i] = tmp;
}
Double[][] eee = new Double[uniqNum+2][uniqNum+1];
Double[][] www = new Double[uniqNum+2][uniqNum+1];
//matrix to store optimal structure
root = new Integer[uniqNum+1][uniqNum+1];
for(int i=1; i<uniqNum+2; i++) {
eee[i][i-1] = 0.0;
www[i][i-1] = 0.0;
}
for(int l=1; l<uniqNum+1; l++) {
for(int i=1; i<=uniqNum-l+1; i++) {
int j = i + l - 1;
eee[i][j] = Double.MAX_VALUE;
www[i][j] = www[i][j-1] + freqsA[j-1];
for(int r=i; r<=j; r++) {
Double t = eee[i][r-1] + eee[r+1][j] + www[i][j];
if(t<eee[i][j]) {
eee[i][j] = t;
root[i][j] = r-1;
}
}
}
}
//total cost
System.out.println(eee[1][uniqNum]);
printTree(1,uniqNum-1,-1, "");
}
public static void printTree(int min, int max, int parent, String s) {
int r = root[min][max];
if(parent == -1 ) {
System.out.println(keysA[r] + " is root");
} else if(min < parent) {
System.out.println(keysA[r] + " is the left child of " + s);
} else {
System.out.println(keysA[r] + " is the right child of " + s);
} if(min < max) {
printTree(min,r,r+1,keysA[r]);
printTree(r+1,max,r,keysA[r]);
}
}
}
My trouble is in the method print tree.

Looks like you aren't checking your bounds correctly. If there is no left or right child, you shouldn't be printing that side. so make sure you check that r+1 is within the array size, and also that a node exists there. do the same for both left and right sides.