diff --git a/week_02/57/AtomicInteger-057.txt b/week_02/57/AtomicInteger-057.txt
new file mode 100644
index 0000000000000000000000000000000000000000..a3111e2b710a67a3f33b4cc8aaec349e02a664bc
--- /dev/null
+++ b/week_02/57/AtomicInteger-057.txt
@@ -0,0 +1,21 @@
+1.原子整形，多线程下保证原子性、可见性。
+private volatile int value;
+用volatile修饰的变量value
+
+2.
+public final boolean compareAndSet(int expect, int update) {
+        return unsafe.compareAndSwapInt(this, valueOffset, expect, update);
+    }
+采用CAS原来，调用Usafe方法，保证操作的原子性
+
+3.
+关于compareAndSet及weakCompareAndSet的一些区别：参考下面的链接
+https://www.jianshu.com/p/55a66113bc54
+
+4.
+public final int getAndIncrement() {
+        return unsafe.getAndAddInt(this, valueOffset, 1);
+    }
+保证原子操作的num++  	
+
+其他方法类似
\ No newline at end of file
diff --git a/week_02/57/AtomicStampedReference-057.txt b/week_02/57/AtomicStampedReference-057.txt
new file mode 100644
index 0000000000000000000000000000000000000000..656c9661a1479c3ef94d1e819b0e43d2f7f25b5d
--- /dev/null
+++ b/week_02/57/AtomicStampedReference-057.txt
@@ -0,0 +1,17 @@
+1.带时间戳的原子引用类型，初始化时必须指定引用类型的初始值及初始版本号
+2. public V getReference() {
+        return pair.reference;
+    }
+	
+	public int getStamp() {
+        return pair.stamp;
+    }
+	
+获取引用及版本号的方法	
+
+3.public V get(int[] stampHolder) {
+        Pair<V> pair = this.pair;
+        stampHolder[0] = pair.stamp;
+        return pair.reference;
+    }
+获取引用类型的值	
\ No newline at end of file
diff --git a/week_02/57/LongAdder-057.txt b/week_02/57/LongAdder-057.txt
new file mode 100644
index 0000000000000000000000000000000000000000..4e8f05a20cff7199c637f92b3a7a99b4f69b11f6
--- /dev/null
+++ b/week_02/57/LongAdder-057.txt
@@ -0,0 +1,62 @@
+1.原子Long类型
+2.
+public LongAdder() {
+    }
+只提供无参构造方法，创建一个初始和为零的新加法器。
+3.
+继承Striped64	
+
+4.add 添加给定值
+public void add(long x) {
+        Cell[] as; long b, v; int m; Cell a;
+        if ((as = cells) != null || !casBase(b = base, b + x)) {
+            boolean uncontended = true;
+            if (as == null || (m = as.length - 1) < 0 ||
+                (a = as[getProbe() & m]) == null ||
+                !(uncontended = a.cas(v = a.value, v + x)))
+                longAccumulate(x, null, uncontended);
+        }
+    }
+	
+5.sum 返回当前总和。返回当前总和。
+返回的值不是原子快照。在没有并发更新的情况下调用会返回准确的结果，
+但是在计算总和时发生的并发更新可能不会合并。
+public long sum() {
+        Cell[] as = cells; Cell a;
+        long sum = base;
+        if (as != null) {
+            for (int i = 0; i < as.length; ++i) {
+                if ((a = as[i]) != null)
+                    sum += a.value;
+            }
+        }
+        return sum;
+    }
+
+6.reset 重置为初始化值，即0
+public void reset() {
+        Cell[] as = cells; Cell a;
+        base = 0L;
+        if (as != null) {
+            for (int i = 0; i < as.length; ++i) {
+                if ((a = as[i]) != null)
+                    a.value = 0L;
+            }
+        }
+    }	
+	
+7.sum() 并reset()
+public long sumThenReset() {
+        Cell[] as = cells; Cell a;
+        long sum = base;
+        base = 0L;
+        if (as != null) {
+            for (int i = 0; i < as.length; ++i) {
+                if ((a = as[i]) != null) {
+                    sum += a.value;
+                    a.value = 0L;
+                }
+            }
+        }
+        return sum;
+    }	
\ No newline at end of file
diff --git a/week_02/57/Unsafe-057.txt b/week_02/57/Unsafe-057.txt
new file mode 100644
index 0000000000000000000000000000000000000000..a1442d1f1f9ce6b1309aa56a8056ab602961ce3c
--- /dev/null
+++ b/week_02/57/Unsafe-057.txt
@@ -0,0 +1,17 @@
+1.
+Unsafe类存在于 sun.misc 包中，其内部方法操作可
+以像C的指针一样直接操作内存。
+Unsafe类中的所有方法都是native修饰的，也就是说Unsafe类中的方法都直接调用操作系统底层资源执
+行相应任务
+
+2.
+public final int getAndAddInt(Object var1, long var2, int var4) {
+        int var5;
+        do {
+            var5 = this.getIntVolatile(var1, var2);
+        } while(!this.compareAndSwapInt(var1, var2, var5, var5 + var4));
+
+        return var5;
+    }
+	
+以其中一个方法为例。经典的自旋锁，实现原子操作的关键。	
\ No newline at end of file