Java四则运算

package androidtextfirst;

import java.util.Random;

import javax.swing.JOptionPane;

public class schooltext2 {

public static void main(String[] args) {
int m = 1;
int a = 0, b = 0, c = 0, d = 0, e = 0;
int x = 0;
String p = "", q = "";
Random random = new Random();

for (int w = 0; w < 1000000000; w++) {
String input = JOptionPane.showInputDialog("请输入选择：1、整数 2、真分数 3、退出程序");
x = Integer.parseInt(input);
if (x == 1) {
for (int i = 0; i < 300; i++) {
a = random.nextInt(99);
b = random.nextInt(99);
c = random.nextInt(3);
if (c == 0) {
System.out.println(a + "+" + b + "=");
}
if (c == 1) {
System.out.println(a + "-" + b + "=");
}
if (c == 2) {
System.out.println(a + "*" + b + "=");
}
if (c == 3) {
if (b != 0) {
System.out.println(a + "/" + b + "=");
}
if (b == 0) {
i--;
}
}

}
}
if (x == 2) {
for (int r = 0; r < 300; r++) {
a = random.nextInt(99);
b = random.nextInt(99);
d = random.nextInt(99);
e = random.nextInt(99);
c = random.nextInt(3);
if ((a >= b && b != 0) || a == 0) {
p = a + "/" + b;
} else {
p = b + "/" + a;
}
if ((d >= e && e != 0) || d == 0) {
q = d + "/" + e;
} else {
q = e + "/" + d;
}
if (c == 0) {
System.out.println(p + "+" + q);
}
if (c == 1) {
System.out.println(p + "-" + q);
}
if (c == 2) {
System.out.println(p + "*" + q);
}
if (c == 3) {
if (d == 0 || e == 0) {
r--;
} else {
System.out.println(p + "/" + q);
}
}
}
}
if (x == 3) {
break;
}
}
}
}