Frame6.java

package lesson3;

public class Frame6 {

	public static void main(String[] args) {
		
		int [] data1 = {1, 10, 5, 7, 6};
		int [] data2 = {0};
		int [] data3 = {};
		int [] data4 = {0, 0, 15, 25, 16};
		int [] data5 = {-3, 25, 2};
		System.out.println(getLast(data1));
		System.out.println(getLast(data2));
		System.out.println(getLast(data3));
		System.out.println(getLast(data4));
		System.out.println(getLast(data5));
	}
	
	static int getLast(int[] data) {
		
		if (data.length > 0) {
			return data[data.length-1];
		}
		else return -1;
	}
}

Frame8.java

package lesson3;

public class Frame8 {

	public static void main(String[] args) {
		
		int[] data = {1, 55, 83, 0};
		int[] data2 = {};
		swap(data, 1, 2);
		swap(data2, 7, 9);
	}
	
	static void swap(int [] data, int i, int k) {
		
		if (i <= data.length && k <= data.length && data != null && i >= 0 && k >= 0) {
			System.out.println("before : " + data[i] + " " + data[k]);
			int temp = data[i];
			data[i] = data[k];
			data[k] = temp;
			System.out.println("after : " + data[i] + " " + data[k]);
		}
	}
}

Frame9.java

package lesson3;

import java.util.Arrays;

public class Frame9 {

	public static void main(String[] args) {
		
		int[] data1 = {8, 9, 0};
		int[] data2 = {};
		printArray(data1);
		printArray(data2);
	}
	
	static void printArray(int[] data) {
		
		System.out.println(Arrays.toString(data));
	}
}