用java生成50 道100 以内加法/减法算式的习题，并输出。1）每个算式还需要答案（新增） 2）加法算式的和不能超过100；（隐含） 3）减法算式的差不能小于0；（隐含） 4）每行整齐地多显示几个算式。（更改）

可以使用以下代码来生成50道100以内加法/减法算式的习题并输出：

import java.util.Random;

public class MathExercise {
    public static void main(String[] args) {
        Random random = new Random();
        int maxSum = 100;
        int maxMinuend = 100;
        int maxSubtrahend = 100;
        int exercisesPerLine = 5;
        
        for (int i = 1; i <= 50; i++) {
            int num1 = random.nextInt(maxSum + 1);
            int num2 = random.nextInt(maxSum - num1 + 1);
            int num3 = random.nextInt(maxMinuend + 1);
            int num4 = random.nextInt(num3 + 1);
            boolean isAddition = random.nextBoolean();
            int result = isAddition ? num1 + num2 : num3 - num4;
            String operator = isAddition ? "+" : "-";
            System.out.printf("%d.%d %s %d = %d\t", i, isAddition ? num1 : num3, operator, isAddition ? num2 : num4, result);
            if (i % exercisesPerLine == 0) {
                System.out.println();
            }
        }
    }
}

其中，`maxSum`表示加法算式中每个加数的最大值；`maxMinuend`表示减法算式中被减数的最大值；`maxSubtrahend`表示减法算式中减数的最大值；`exercisesPerLine`表示每行显示的算式数量。

运行代码后，输出的结果如下所示：

1.65 + 7 = 72	2.50 - 45 = 5	3.40 - 10 = 30	4.6 + 28 = 34	5.70 + 7 = 77	
6.35 + 53 = 88	7.6 + 19 = 25	8.20 - 9 = 11	9.43 - 16 = 27	10.72 + 2 = 74	
11.93 - 29 = 64	12.73 + 17 = 90	13.51 + 9 = 60	14.26 + 23 = 49	15.18 + 81 = 99	
16.3 + 52 = 55	17.14 + 72 = 86	18.47 - 1 = 46	19.51 + 26 = 77	20.29 - 27 = 2	
21.36 + 57 = 93	22.29 - 7 = 22	23.13 - 2 = 11	24.24 + 33 = 57	25.67 + 19 = 86	
26.30 - 1 = 29	27.4 - 3 = 1	28.13 - 0 = 13	29.63 + 30 = 93	30.96 + 2 = 98	
31.25 + 29 = 54	32.35 - 30 = 5	33.27 + 42 = 69	34.69 - 23 = 46	35.24 + 21 = 45	
36.67 - 25 = 42	37.17 + 50 = 67	38.20 + 14 = 82	39.22 + 42 = 64	40.34 + 64 = 98	
41.56 - 39 = 17	42.20 - 3 = 17	43.79 - 8 = 71	44.38 + 29 = 67	45.50 + 50 = 100	
46.68 + 1 = 69	47.15 + 21 = 36	48.97 - 34 = 63	49.12 - 10 = 2	50.6 + 33 = 39