Description

Key Content
• Understand the concept that passing code to methods with behavior parameterization.
• Understand the necessity of method reference and lambda.
• Learn how to use important functional interface.

Before Exercise
Here is a question from Assignment2 of CS102A 2018Fall.
Sort

Description:
Given an array, you should output the indices of elements according their values from small to large. For example, here is an array [2, 1, 3, 4], element 1 is the smallest one, its index is 1, so the first output is 1, element 2 is the second smallest, its index is 0, so the second output is 0, and so on. The output of array [2,1,3,4] is [1,0,2,3]. If some elements have the same value, according their indices from small to large. For example, the output of array [2,2,2,2] is [0,1,2,3]. When you print the result, you should follow the format according to the Output description.

Input:
The first line will be an integer T (1<=T<=20), which is the number of test cases.
For each test case, the first line will be the size of the array N (1 <= N<= 1000).
The second line contains N integers, each integer ai is in range: [-2^30,2^30].

Output:
The indices in output should be separated by a space.

Sample Input:
1
9
5 3 66 22 9 1 77 88 99

Sample Output:
5 1 0 4 3 2 6 7 8

And here is a reference code:
import java.util.Scanner;

public class Sort { public static void main(String[] args) { Scanner in = new Scanner(System.in); int total = in.nextInt();

while (total– > 0) { int n = in.nextInt(); int array[] = new int[n]; int index[] = new int[n]; for (int i = 0; i < n; i++) {
array[i] = in.nextInt(); index[i] = i;
}
//Bubble sort the index according the value
int temp;
for (int i = 0; i < n; i++) {
for (int j = 0; j < n – i – 1; j++) {

if (array[index[j]] > array[index[j+1]]){ temp = index[j + 1]; index[j + 1] = index[j];
index[j] = temp;

}
}
}

for (int i = 0; i < n; i++) { System.out.printf(“%d”, index[i]);
if (i != n – 1) System.out.print(” “);
}

1. Rewrite above code using Collections.sort().
2. If we want to output the indices of elements according their values from large to small, what we should do?

3. If add an input argument, 0 means to arrange the element from small to large, 1 means to arrange the element from large to small, what we should do?

1. Sort1.java
2. Sort2.java
3. Sort3.java

Exercise
1. Given an integer array, please do following tasks:
(1) output all even numbers in the array.

You should try to use Predicate<T> interface.
2. Give a sequence of integer numbers, output their quadratic sum.

You should try to use UnaryOperator<T>, Function<T, R> or BinaryOperator<T>.