For each program below, show what is displayed on the screen when the code executes. import java.util.Arrays; public class ReferenceSemantics1
{
public static int mystery(int a, int [] b)
{
a++;
b[0] = 0;
b = new int[4];
return a / 2;
}
public static void main(String [] args)
{
int x = 10;
int [] y = {3, -3, 3};
x = x + mystery(x, y);
System.out.println(x);
System.out.println(Arrays.toString(y));
}
} screen
15
[0, -3, 3] import java.awt.Point; public class ReferenceSemantics2
{
public static int mystery(char a, Point b)
{
a = (char) (a + 1);
b.setLocation(0, 2);
b = new Point(1, 3);
return b.x;
}
public static void main(String [] args)
{
char x = 'b';
Point y = new Point(5, 7);
y.y = mystery(x, y);
System.out.println(x);
System.out.println(y);
}

} screen b java.awt.Point[x=0,y=1] import java.io.File; public class ReferenceSemantics3
{
public static void mystery(boolean a, File f)
{
a = !a;
f.delete(); // this deletes the file (whose name is stored in f)
// from the hard drive, if it exists.
f = new File("output");
return;
}
public static void main(String [] args)
{
boolean x = false;
File y = new File("input");
mystery(x, y);
System.out.println(x);
System.out.println(y.getName());
}
} screen false input public class NestedCalls1
{
public static void mystery1(int a)
{
System.out.println("m 1");
if(a > 0) {
mystery2(-a);
System.out.println("here?");
}
System.out.println("and here?");
}
public static void mystery2(int b)
{
System.out.println("m 2");
if(b > 0) {
System.out.println("here 2?");
mystery1(b – 10);

}
System.out.println("and here 2?");
}
public static void main(String [] args)
{
System.out.println("main");
int x = 3;
mystery1(x);
mystery2(x);
System.out.println("what about here?");
}
} screen main m 1 m 2 and here 2? here? and here? m 2 here 2? m 1 and here? and here 2? what about here? public class NestedCalls2
{
public static int mystery1(int a)
{
System.out.println("m 1");
return a / 2;
}
public static String mystery2(int b)
{
String s = "m 2";
System.out.println(s);
for(int i=0; i<b ; i++) {
s = s + " " + i;
}
return s;
}
public static void main(String [] args)
{
System.out.println("main");
System.out.println(mystery2(mystery1(4)));
System.out.println("end main");
}
}

screen main m 1 m 2 m 2 0 1 end main
a.
Write a method that takes an integer A as an argument. The method should display the value of A squared on the screen.
// for these kinds of questions, you only need to write the method definition
// you do NOT need to write the import statements, or "public class <name>" public static void displaySquare(int A)
{
System.out.println("the square of " + A + " is " + (A * A));
} b.
Write a method that takes an integer N as an argument. The method should display a line with N copies of the '*' character on the screen. public static void displayLineOfStars(int N)
{
for(int i=0; i<N; i++) {
System.out.print("*");
}
System.out.println();
} c.
Write a method that takes two Strings, s1 and s2, as arguments. The method should return whether s1 contains a copy of s2 inside it. public static boolean stringContainsOtherString(String s, String other)
{
// I check this first to avoid a NullPointerException below
if(s1==null) {
return false; // null String can't contain anything inside of it
}
if(s1.indexOf(s2) >= 0) {
return true; // found s2 inside of s1, so return true
}
return false; // couldn't find s2 inside of s1, so return false
}

d.
Write a method that takes two Points, p1 and p2, and a double d as arguments. The method should return whether the distance between p1 and p2 is less than d. public static boolean distanceIsLessThan(Point p1, Point p2, double d)
{
// notice that this will cause a NullPointerException if p1 is null
// Unlike the example above, it's not clear what the method should return
// if p1 is null. So here it's often better to just let the program
// crash if p1 is null; the method calling this one will need to make
// sure that p1 is not null before calling this method.
double dist = p1.distance(p2);
return dist < d;
// alternatively, you could say if(dist<d) return true; else return false;
// the two versions are equivalent. Can you figure out why?
} e.
Write a method that takes an array of chars A, an integer j, and an integer k as arguments.
The method should return a String consisting of the characters in A between positions j and k. public static String subCharArray(char [] A, int j, int k)
{
String ret = "";
for(int i=j; i<k; i++)
{
ret = ret + char[i];
}
return ret;
}