Optional

src/main/java/com/zeekling/optional/Java8Tester.java

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+package com.zeekling.optional;
+
+import java.util.Optional;
+
+/**
+ * @author zeekling
+ * @apiNote Optional 实例
+ * @since 2021-06-20
+ */
+public class Java8Tester {
+
+
+    public static void main(String args[]){
+
+        Java8Tester java8Tester = new Java8Tester();
+        Integer value1 = null;
+        Integer value2 = new Integer(10);
+
+        // Optional.ofNullable - 允许传递为 null 参数
+        Optional<Integer> a = Optional.ofNullable(value1);
+
+        // Optional.of - 如果传递的参数是 null，抛出异常 NullPointerException
+        Optional<Integer> b = Optional.of(value2);
+        System.out.println(java8Tester.sum(a,b));
+    }
+
+    public Integer sum(Optional<Integer> a, Optional<Integer> b){
+
+        // Optional.isPresent - 判断值是否存在
+
+        System.out.println("第一个参数值存在: " + a.isPresent());
+        System.out.println("第二个参数值存在: " + b.isPresent());
+
+        // Optional.orElse - 如果值存在，返回它，否则返回默认值
+        Integer value1 = a.orElse(new Integer(0));
+
+        //Optional.get - 获取值，值需要存在
+        Integer value2 = b.get();
+        return value1 + value2;
+    }
+
+}