// Initializing array of integers 
        Integer[] num = { 2, 4, 7, 5, 9 }; 

  // using Collections.max() to find minimum element 
        // using only 1 line. 
int max = Collections.max(Arrays.asList(num)); 

You can simply used in-build java Collection and Arrays to sort out this problem. You just need to import them and use it.

Please check below code.

import java.util.Arrays;
import java.util.Collections;

public class getMinNMax {
    public static void main(String[] args) {

        Integer[] num = { 2, 11, 55, 99 };

        int min = Collections.min(Arrays.asList(num));
        int max = Collections.max(Arrays.asList(num));

        System.out.println("Minimum number of array is : " + min);
        System.out.println("Maximum number of array is : " + max);
    }
}

int[] convertedValues = new int[10];
int max = convertedValues[0];

for (int i = 1; i < convertedValues.length; i++) {
    if (convertedValues[i] > max) {
        max = convertedValues[i];
    }
}

Similarly find for the minimum value by changing lesser symbol.

You can simply use the new Java 8 Streams but you have to work with int.

The stream method of the utility class Arrays gives you an IntStream on which you can use the min method. You can also do max, sum, average,...

The getAsInt method is used to get the value from the OptionalInt

import java.util.Arrays;

public class Test {
    public static void main(String[] args){
        int[] tab = {12, 1, 21, 8};
        int min = Arrays.stream(tab).min().getAsInt();
        int max = Arrays.stream(tab).max().getAsInt();
        System.out.println("Min = " + min);
        System.out.println("Max = " + max)
    }

}

==UPDATE==

If execution time is important and you want to go through the data only once you can use the summaryStatistics() method like this

import java.util.Arrays;
import java.util.IntSummaryStatistics;

public class SOTest {
    public static void main(String[] args){
        int[] tab = {12, 1, 21, 8};
        IntSummaryStatistics stat = Arrays.stream(tab).summaryStatistics();
        int min = stat.getMin();
        int max = stat.getMax();
        System.out.println("Min = " + min);
        System.out.println("Max = " + max);
    }
}

This approach can give better performance than classical loop because the summaryStatistics method is a reduction operation and it allows parallelization.