arraylist.get(i)= arraylist.get(i);arraylist.get(j) =tmp;

您不能为方法调用赋值.正如编译器告诉你的，赋值的左边必须是一个变量.

使用set方法:

arraylist.set(i,arraylist.get(j));arraylist.set(j,tmp);

有没有不使用 set 方法的方法?

没有.除非您希望将 ArrayList 转换为数组，否则请对数组进行排序，然后使用排序后的数组更新 ArrayList.

ArrayList < Integer > arraylist = new ArrayList < Integer > ();

arraylist.add(10010);
arraylist.add(5);
arraylist.add(4);
arraylist.add(2);

for (int i = 0; i < arraylist.size(); i++) {

    for (int j = arraylist.size() - 1; j > i; j--) {
        if (arraylist.get(i) > arraylist.get(j)) {

            int tmp = arraylist.get(i);
            arraylist.get(i) = arraylist.get(i);
            arraylist.get(j) = tmp;

        }

    }

}
for (int i: arraylist) {
    System.out.println(i);
}

It is giving error while swapping, The LHS should be variable. I understand it. Set method works here but I do not want to use. Is there a way to do it without using set method? Help is really appreciated.

arraylist.get(i)= arraylist.get(i);
arraylist.get(j) =tmp;

You can't assign a value to a method call. As the compiler told you, the left hand side of an assignment must be a variable.

Use set method :

arraylist.set(i,arraylist.get(j));
arraylist.set(j,tmp);

Is there a way to do it without using set method?

No. Unless you wish to convert your ArrayList to an array, sort the array, and update the ArrayList with the sorted array.