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SortRationalsWithLambdas.java
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SortRationalsWithLambdas.java
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package edu.ucsb.cs56.pconrad.rational;
import java.util.ArrayList;
import java.util.Comparator;
/**
Example of sorting Rationals with lambdas
*/
public class SortRationalsWithLambdas {
public static String toStringWithDecimals(ArrayList<Rational> nums) {
String result = "[";
for (int i = 0; i<nums.size(); i++) {
result += (i==0) ? "" : ",";
result += new RealApproximationR2S().r2s(nums.get(i));
}
result += "]";
return result;
}
public static ArrayList<Rational> makeRationalArrayListFromStrings( String [] strings) {
ArrayList<Rational> nums = new ArrayList<Rational>();
for (String s: strings) {
nums.add(new Rational(s));
}
return nums;
}
/**
Comparator that orders first by denominator, then by numerator, e.g.
<code>1, 2, 3, -5/2, 1/2, 3/2, 5/2, -7/3, 1/3, 2/3, 4/3</code>.
The comparator is initialized with a Lambda Expression
*/
public static final Comparator<Rational> denomThenNum = (r1,r2) -> {
int r1num = r1.getNumerator();
int r2num = r2.getNumerator();
int r1denom = r1.getDenominator();
int r2denom = r2.getDenominator();
if (r1denom==r2denom) {
return r1num - r2num;
} else {
return r1denom - r2denom;
}
};
public static void demonstrateSortingAndPrinting(ArrayList<Rational> nums) {
System.out.println("Before sorting = \n" + nums);
System.out.println(" as decimals = \n" + toStringWithDecimals(nums));
java.util.Collections.sort(nums);
System.out.println("After sort with Collections.sort(nums) = \n" + nums);
System.out.println(" as decimals = \n" + toStringWithDecimals(nums));
nums.sort(denomThenNum);
System.out.println("After nums.sort(denomThenNum) = \n" + nums);
System.out.println(" as decimals = \n" + toStringWithDecimals(nums));
nums.sort( (r1, r2)->r1.compareTo(r2));
System.out.println("After nums.sort((r1,r2)->r1.compareTo(r2)) = \n" + nums);
System.out.println(" as decimals = \n" + toStringWithDecimals(nums));
}
public static void main(String args[]) {
String [] strings1 = new String [] { "1/3", "-2/3", "4/5", "7/2", "8/9", "2/1", "8/1", "1/9", "-8/9", "3/7" };
ArrayList<Rational> nums = makeRationalArrayListFromStrings(strings1);
demonstrateSortingAndPrinting(nums);
}
}