java.util.function
Supplier
仅含一个无参的方法，称为生产型接口，指定接口是什么泛型，get方法就返回什么类型的数据
T get()：获取泛型参数指定类型的对象数据
public static String getString(Supplier sup) {
return sup.get();
}
public static void main(String[] args) {
String s = getString(() -> {
return "123";
});
System.out.println(s);
} 案例
public static int getMax(Supplier sup) {
return sup.get();
}
public static void main(String[] args) {
int[] arr1 = {2,323, -3434, 543, 23232, 23, -65};
int maxValue = getMax(() -> {
int max = arr1[0];
for (int i : arr1) {
if (i > max) {
max = i;
}
}
return max;
});
System.out.println(maxValue);
} Consumer
消费一个指定泛型的数据,是一个消费型接口，
抽象：void accpet(T t)
泛型执行什么类型，就可用accept方法消费什么类型的数据
public static void method(String name, Consumer con) {
con.accept(name);
}
public static void main(String[] args) {
method("wan", (String name) -> {
System.out.println(name);
});
} 默认方法：
andThen
需要两个Consumer接口，可以把两个Consumer接口组合到一起，再对数据进行消费 
public static void method(String name, Consumer con1, Consumer con2) {
con1.andThen(con2).accept(name);
}
public static void main(String[] args) {
method("hello", (t) -> {
System.out.println(t.toUpperCase());
}, (t) -> {
System.out.println(t.toLowerCase());
});
} public static void method(String[] arr, Consumer con1, Consumer con2) {
for (String message : arr) {
con1.andThen(con2).accept(message);
}
}
public static void main(String[] args) {
String[] arr = {"dili, girl", "zz, girl",
"hehei, male"};
method(arr, (message)-> {
String name = message.split(",")[0];
System.out.print("name：" + name);
}, (message) -> {
String sexy = message.split(",")[1];
System.out.println("、性别：" + sexy + "。");
});
} 案例
public static void method(String[] arr, Consumer con1, Consumer con2) {
for (String message : arr) {
con1.andThen(con2).accept(message);
}
}
public static void main(String[] args) {
String[] arr = {"dili, girl", "zz, girl",
"hehei, male"};
method(arr, (message)-> {
String name = message.split(",")[0];
System.out.print("name：" + name);
}, (message) -> {
String sexy = message.split(",")[1];
System.out.println("、性别：" + sexy + "。");
});
} 和下列代码同理（上代码仅仅是用了andThen方法，有什么优点？？？）
public static void method(String[] arr, Consumer con1) {
for (String message : arr) {
con1.accept(message);
}
}
public static void main(String[] args) {
String[] arr = {"dili, girl", "zz, girl",
"hehei, male"};
method(arr, (message) -> {
String[] ms = message.split(",");
System.out.println("姓名：" + ms[0] + "..." + "性别：" + ms[1]);
});
} Predicate
对某种数据类型进行判断，返回一个boolean值
抽象方法：
boolean test(T t)
public static boolean checkString(String s, Predicate pre) {
return pre.test(s);
}
public static void main(String[] args) {
String s = "abcde";
//()中有没有参数，观察test方法中是否有参数
boolean b = checkString(s, (String str) -> {
return str.length() > 5;
});
System.out.println(b);
} 默认方法：
and
public static boolean checkString(String s, Predicate pre1, Predicate pre2) {
return pre1.and(pre2).test(s);
}
public static void main(String[] args) {
String s = "abcde12";
boolean b = checkString(s, (String str) -> {
return str.length() > 5;
}, (String str) -> {
return str.contains("a");
});
System.out.println(b);
} or
public static boolean checkString(String s, Predicate pre1, Predicate pre2) {
return pre1.or(pre2).test(s);
}
public static void main(String[] args) {
String s = "abc2";
boolean b = checkString(s, (String str) -> {
return str.length() > 5;
}, (String str) -> {
return str.contains("a");
});
System.out.println(b);
} negate
public static boolean checkString(String s, Predicate pre1) {
return pre1.negate().test(s);
}
public static void main(String[] args) {
String s = "abc2";
boolean b = checkString(s, (String str) -> {
return str.length() > 5;
});
System.out.println(b);
} 案例
public static ArrayList checkString(String[] arr, Predicate pre1, Predicate pre2) {
ArrayList list = new ArrayList<>();
for (String str : arr) {
boolean b = pre1.and(pre2).test(str);
if (b) {
list.add(str);
}
}
return list;
}
public static void main(String[] args) {
String[] arr = {"wan, girl", "zzz, girl",
"cccc, girl", "zzz, man"};
ArrayList b = checkString(arr, (String str) -> {
String name = str.split(", ")[0];
return name.length() == 3;
}, (String str) -> {
String sexy = str.split(", ")[1];
return sexy.equals("girl");
});
System.out.println(b.toString());
} Function
apply();
根据T的类型，将T的类型转换为R的类型
public static void change(String s, Function fun) {
Integer in = fun.apply(s);
System.out.println(in);
}
public static void main(String[] args) {
String s = "1234";
change(s, (String str) -> {
//这段代码相当于是重写apply方法
//传递参数要看apply里包含什么，代码目的
return Integer.parseInt(str);
});
} andThen()
组合操作
public static void change(String s, Function fun1,
Function fun2) {
String stringOut = fun1.andThen(fun2).apply(s);
System.out.println(stringOut);
}
public static void main(String[] args) {
String s = "1234";
change(s, (String str) -> {
return Integer.parseInt(str) + 10;
}, (Integer num) -> {
return num + "";
});
} 案例
public static int change(String s, Function fun1,
Function fun2, Function fun3) {
return fun1.andThen(fun2.andThen(fun3)).apply(s);
}
public static void main(String[] args) {
String s = "zz 30";
int ss = change(s, (String str) -> {
return str.split(" ")[1];
}, (String str1) -> {
return Integer.parseInt(str1);
}, (Integer num) -> {
return num + 100;
});
System.out.println(ss);
}