java数组的另一种用法

import java.io.Serializable;

public enum SafeSingleton implements Serializable{
	INSTANCE;
	SafeSingleton(){
		//
	}
	
	public void singleton(){
		System.out.println("hello!!");
	}
}
	@Test
	public void test16() {
		// Collections2.filter(unfiltered, predicate);
		SafeSingleton.INSTANCE.singleton();
	}

package guava;

public enum Operation {
	PLUS {
		double eval(double x, double y) {
			return x + y;
		}
	},
	MINUS {
		double eval(double x, double y) {
			return x - y;
		}
	},
	TIMES {
		double eval(double x, double y) {
			return x * y;
		}
	},
	DIVIDE {
		double eval(double x, double y) {
			return x / y;
		}
	};

	abstract double eval(double x, double y);
}
	@Test
	public void test(){
		double eval = Operation.DIVIDE.eval(12, 2);
		System.out.println(eval);
	}