学习1

huguiqi · huguiqi · commit a563e213d3a2 · 2022-03-13T00:57:49.000+08:00
diff --git a/src/main/java/lambdasinaction/chap1/learn/FilteringRepeatElemetes.java b/src/main/java/lambdasinaction/chap1/learn/FilteringRepeatElemetes.java
@@ -0,0 +1,42 @@
+package lambdasinaction.chap1.learn;
+
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import java.util.function.Predicate;
+import java.util.stream.Collectors;
+
+public class FilteringRepeatElemetes {
+
+    //将重复的数据取出来,有几种方法
+    private static List elems = Arrays.asList("b","e","d","c","b","a","a","c","b","a");
+
+    public static void main(String ... args) {
+
+        long start = System.currentTimeMillis();
+        List<String> repeatList = filterRepeat(elems,new PredicateRepeatElement<String>());
+        System.out.println(repeatList.toString());
+        System.out.println((System.currentTimeMillis() - start) + "ms");
+    }
+
+
+    public static List<String> filterRepeat(List<String> elems, Predicate<String> p){
+        return elems.stream().filter(e-> p.test(e)).collect(Collectors.toList());
+    }
+
+    private static class PredicateRepeatElement<T> implements Predicate<String> {
+        private Set<String> hashSet = new HashSet<>();
+
+
+        @Override
+        public boolean test(String s) {
+            if (hashSet.contains(s)){
+                return true;
+            }else {
+                hashSet.add(s);
+                return false;
+            }
+        }
+    }
+}
