How to determine if there are duplicate elements in Java

Given an integer array, determine whether there are duplicate elements. The function returns true if any value appears at least twice in the array. Returns false if every element in the array is different.

示例 1:
输入: [1,2,3,4]
输出: true

Method 1: Sorting time complexity is O (NlogN) space complexity is O (logN)

nums.sort()
for i in range(len(nums)-1):
    #判断前一个与后一个数是否相等
    if nums[i] == nums[i+1]:
        return  True
return False

Method 2: Hash table

dic = {}
for i in range(len(nums)):
    if nums[i] in dic:
        return True
    else:
        dic[nums[i]] = 1
return False

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