a==b,b==c都为true，那a==c一定为true吗？？？

问题一：

int a = 50;
Integer a1 = 50;
Integer b1 = 50;
Integer c1 = 100;
Integer d1 = a1 + b1;

System.out.println(a == a1);
System.out.println(a == b1);
System.out.println(a1 == b1);
System.out.println(c1 == (a1 + b1));
System.out.println(c1 == d1);

问题二：

int a = 100;
Integer a1 = 100;
Integer b1 = 100;
Integer c1 = 200;
Integer d1 = a1 + b1;

System.out.println(a == a1);
System.out.println(a == b1);
System.out.println(a1 == b1);
System.out.println(c1 == (a1 + b1));
System.out.println(c1 == d1);

问题三：

int a = 200;
Integer a1 = 200;
Integer b1 = 200;
Integer c1 = 400;
Integer d1 = a1 + b1;

System.out.println(a == a1);
System.out.println(a == b1);
System.out.println(a1 == b1);
System.out.println(c1 == (a1 + b1));
System.out.println(c1 == d1);

问题四：

double a = 50d;
Double a1 = 50d;
Double b1 = 50d;
Double c1 = 100d;
Double d1 = a1 + b1;

System.out.println(a == a1);
System.out.println(a == b1);
System.out.println(a1 == b1);
System.out.println(c1 == (a1 + b1));
System.out.println(c1 == d1);

问题五：

double a = 200d;
Double a1 = 200d;
Double b1 = 200d;
Double c1 = 400d;
Double d1 = a1 + b1;

System.out.println(a == a1);
System.out.println(a == b1);
System.out.println(a1 == b1);
System.out.println(c1 == (a1 + b1));
System.out.println(c1 == d1);

问题六：

double a = 0.1d;
double b = 0.2d;
double c = 0.3d;

System.out.println(c == (a + b));
System.out.println(0.3d == (a + b));

问题七：

float a = 0.1f;
float b = 0.2f;
float c = 0.3f;

System.out.println(c == (a + b));
System.out.println(0.3f == (a + b));

问题八：

int a = 0;
int b = 0;

System.out.println(a/b);

问题九：

double a = 0d;
double b = 0d;

System.out.println(a/b);

这里面有太多的我们初始学习时就遇到过的，有的遇到过的不止一遍，面试问到的也不止一遍，为什么到现在，我们还有些题目模棱两可呢，为什么不抽点时间好好看看这方面的知识呢？

答案一

true
true
true
true
true

答案二

true
true
true
true
false

答案三

true
true
false
true
false

答案四

true
true
false
true
false

答案五

true
true
false
true
false

答案六

false
false

答案七

true
true

答案八

java.lang.ArithmeticException: / by zero

答案九

NaN