diff --git a/longest-repeating-character-replacement/donghyeon95.java b/longest-repeating-character-replacement/donghyeon95.java
new file mode 100644
index 000000000..816403dca
--- /dev/null
+++ b/longest-repeating-character-replacement/donghyeon95.java
@@ -0,0 +1,45 @@
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Set;
+
+class Solution {
+	public int characterReplacement(String s, int k) {
+		// K개까지는 용인되는 최대 길이를 구해라
+		// 2 포인터 => 최대 O(2*N) = O(N)
+		// 용인 되는 길이면 second++, 용인되는 길이가 아니면 first++;
+
+		String[] strings = s.split("");
+		HashMap<String, Integer> strCnt = new HashMap<>();
+		int result = 0;
+		int first = 0;
+		int second = 0;
+
+		while(first<s.length()){
+			strCnt.put(strings[first], strCnt.getOrDefault(strings[first], 0)+1);
+			System.out.println(" second: " + second + " first: " + first );
+			if (getOtherCnt(strCnt) <= k) {
+				result = Math.max(result, first-second+1);
+				first++;
+			}
+			else {
+				strCnt.put(strings[second], strCnt.getOrDefault(strings[second],1)-1);
+				strCnt.put(strings[first], strCnt.getOrDefault(strings[first], 0)-1);
+				second++;
+			}
+		}
+
+		return result;
+	}
+
+	public int getOtherCnt(HashMap<String, Integer> strCnt) {
+		int total = 0;
+		int max = 0;
+		for (int a: strCnt.values()) {
+			total += a;
+			max = Math.max(max, a);
+		}
+		return total - max;
+	}
+}
+
+
diff --git a/number-of-1-bits/donghyeon95.java b/number-of-1-bits/donghyeon95.java
new file mode 100644
index 000000000..4a93019b8
--- /dev/null
+++ b/number-of-1-bits/donghyeon95.java
@@ -0,0 +1,15 @@
+class Solution {
+	public int hammingWeight(int n) {
+		int mask = 1;
+		int result = 0;
+		while(n>0) {
+			if ((n & mask) == 1) {
+				result++;
+			}
+			n = n >> 1;
+		}
+
+		return result;
+	}
+}
+