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BAEL-1076 How to get a number of digits in an int? (#2457)

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* BAEL-1076 How to get a number of digits in an int?

Six different ways to find the number of digits in an integer.

* BAEL-1076 How to get a number of digits in an int?

* Update NumberOfDigits.java
This commit is contained in:
ramansahasi
2017-08-26 00:54:43 +05:30
committed by maibin
parent d492c6f4d8
commit 09d10ac85f
4 changed files with 355 additions and 0 deletions
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131
core-java/src/main/java/com/baeldung/numberofdigits/Benchmarking.java Normal file
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package com.baeldung.numberofdigits;
import static com.baeldung.designpatterns.util.LogerUtil.LOG;;
public class Benchmarking {;
private static final int LOWER_BOUND = 1;
private static final int UPPER_BOUND = 999999999;
public static void main(String[] args) {
LOG.info("Testing all methods...");
long length = test_stringBasedSolution();
LOG.info("String Based Solution : " + length);
length = test_logarithmicApproach();
LOG.info("Logarithmic Approach : " + length);
length = test_repeatedMultiplication();
LOG.info("Repeated Multiplication : " + length);
length = test_shiftOperators();
LOG.info("Shift Operators : " + length);
length = test_dividingWithPowersOf2();
LOG.info("Dividing with Powers of 2 : " + length);
length = test_divideAndConquer();
LOG.info("Divide And Conquer : " + length);
}
private static long test_stringBasedSolution() {
long startTime, stopTime, elapsedTime;
startTime = System.currentTimeMillis();
int total = 0;
for (int i = LOWER_BOUND; i <= UPPER_BOUND; i++) {
total += NumberOfDigits.stringBasedSolution(i);
}
stopTime = System.currentTimeMillis();
elapsedTime = stopTime - startTime;
return elapsedTime;
}
private static long test_logarithmicApproach() {
long startTime, stopTime, elapsedTime;
startTime = System.currentTimeMillis();
int total = 0;
for (int i = LOWER_BOUND; i <= UPPER_BOUND; i++) {
total += NumberOfDigits.logarithmicApproach(i);
}
stopTime = System.currentTimeMillis();
elapsedTime = stopTime - startTime;
return elapsedTime;
}
private static long test_repeatedMultiplication() {
long startTime, stopTime, elapsedTime;
startTime = System.currentTimeMillis();
int total = 0;
for (int i = LOWER_BOUND; i <= UPPER_BOUND; i++) {
total += NumberOfDigits.repeatedMultiplication(i);
}
stopTime = System.currentTimeMillis();
elapsedTime = stopTime - startTime;
return elapsedTime;
}
private static long test_shiftOperators() {
long startTime, stopTime, elapsedTime;
startTime = System.currentTimeMillis();
int total = 0;
for (int i = LOWER_BOUND; i <= UPPER_BOUND; i++) {
total += NumberOfDigits.shiftOperators(i);
}
stopTime = System.currentTimeMillis();
elapsedTime = stopTime - startTime;
return elapsedTime;
}
private static long test_dividingWithPowersOf2() {
long startTime, stopTime, elapsedTime;
startTime = System.currentTimeMillis();
int total = 0;
for (int i = LOWER_BOUND; i <= UPPER_BOUND; i++) {
total += NumberOfDigits.dividingWithPowersOf2(i);
}
stopTime = System.currentTimeMillis();
elapsedTime = stopTime - startTime;
return elapsedTime;
}
private static long test_divideAndConquer() {
long startTime, stopTime, elapsedTime;
startTime = System.currentTimeMillis();
int total = 0;
for (int i = LOWER_BOUND; i <= UPPER_BOUND; i++) {
total += NumberOfDigits.divideAndConquer(i);
}
stopTime = System.currentTimeMillis();
elapsedTime = stopTime - startTime;
return elapsedTime;
}
}

97
core-java/src/main/java/com/baeldung/numberofdigits/NumberOfDigits.java Normal file
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package com.baeldung.numberofdigits;
public class NumberOfDigits {
public static int stringBasedSolution(int number) {
int length = String.valueOf(number).length();
return length;
}
public static int logarithmicApproach(int number) {
int length = (int) Math.log10(number) + 1;
return length;
}
public static int repeatedMultiplication(int number) {
int length = 0;
long temp = 1;
while(temp <= number) {
length++;
temp *= 10;
}
return length;
}
public static int shiftOperators(int number) {
int length = 0;
long temp = 1;
while(temp <= number) {
length++;
temp = (temp << 3) + (temp << 1);
}
return length;
}
public static int dividingWithPowersOf2(int number) {
int length = 1;
if (number >= 100000000) {
length += 8;
number /= 100000000;
}
if (number >= 10000) {
length += 4;
number /= 10000;
}
if (number >= 100) {
length += 2;
number /= 100;
}
if (number >= 10) {
length += 1;
}
return length;
}
public static int divideAndConquer(int number) {
if (number < 100000){
// 5 digits or less
if (number < 100){
// 1 or 2
if (number < 10)
return 1;
else
return 2;
}else{
// 3 to 5 digits
if (number < 1000)
return 3;
else{
// 4 or 5 digits
if (number < 10000)
return 4;
else
return 5;
}
}
} else {
// 6 digits or more
if (number < 10000000) {
// 6 or 7 digits
if (number < 1000000)
return 6;
else
return 7;
} else {
// 8 to 10 digits
if (number < 100000000)
return 8;
else {
// 9 or 10 digits
if (number < 1000000000)
return 9;
else
return 10;
}
}
}
}
}

27
core-java/src/main/java/com/baeldung/numberofdigits/NumberOfDigitsDriver.java Normal file
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package com.baeldung.numberofdigits;
import static com.baeldung.designpatterns.util.LogerUtil.LOG;
public class NumberOfDigitsDriver {
public static void main(String[] args) {
LOG.info("Testing all methods...");
long length = NumberOfDigits.stringBasedSolution(602);
LOG.info("String Based Solution : " + length);
length = NumberOfDigits.logarithmicApproach(602);
LOG.info("Logarithmic Approach : " + length);
length = NumberOfDigits.repeatedMultiplication(602);
LOG.info("Repeated Multiplication : " + length);
length = NumberOfDigits.shiftOperators(602);
LOG.info("Shift Operators : " + length);
length = NumberOfDigits.dividingWithPowersOf2(602);
LOG.info("Dividing with Powers of 2 : " + length);
length = NumberOfDigits.divideAndConquer(602);
LOG.info("Divide And Conquer : " + length);
}
}