Java空格引发的编译错误

int a = 1;
a+ = 1;

提示错误：Syntax error on tokens, they can be merged to form +=

加号和等号之间存在一个空格，这样就会编译不通过，类似的还有：

if(a! =1){
    //TO DO
}

提示错误：Syntax error on tokens, they can be merged to form !=