//: reusing/FinalData.java

// The effect of final on fields

package com.reusing07;

import java.util.Random;

class Value {

int i; // Package access

public Value(int i) {

this.i = i;

}

}

public class FinalData {

private static Random rand = new Random(50);

private String id;

public FinalData(String id) { this.id = id; }

// Can be compile-time constants:

private final int valueOne = 9;

private static final int VALUE_TWO = 99;

// Typical public constant

public static final int VALUE_THREE = 39;

// Cannot be compile-time constants

private final int i4 = rand.nextInt(20);

static final int INT_5 = rand.nextInt(20);

private Value v1 = new Value(11);

private final Value v2 = new Value(22);

private static final Value v3 = new Value(33);

// Arrays:

private final int[] a = { 1, 2, 3, 4, 5, 6 };

public String toString() {

return id + ": " + "i4 = " + i4 + ", INT_5 = " + INT_5;

}

public static void main(String[] args) {

// TODO Auto-generated method stub

// final 基本类型，数据无法改变

// final 对象（数组也是对象），不能改变引用

// final static final 类第一次初始化，后面的类对象初始化值也不变

FinalData fd1 = new FinalData("fd1");

//! fd1.valueOne++; // Error: can't change value

fd1.v2.i++; // Object is not constant!

fd1.v1 = new Value(9); // OK -- not final

for(int i = 0; i < fd1.a.length; i++) {

fd1.a[i]++; // Object is not constants

}

//! fd1.v2 = new Value(0); // change reference

//! fd1.a = new int[3];

System.out.println(fd1);

System.out.println("Creating new FinalData");

FinalData fd2 = new FinalData("fd2");

System.out.println(fd1);

System.out.println(fd2);

}

}