数组、容器类（List\Set\Map）等的toString方法

<pre name="code" class="java">import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.omg.CosNaming.NamingContextExtPackage.AddressHelper;

// 8基本类型和包装类 、String类，其toString已做过重载，因此能够打印出值
// 自定义类（如下面的B及其子类），需要重载其toString方法，才能够打印出非默认的值
// 其中，Object类中toString的默认值是“包名.类名@哈希值”</span></strong>

public class Test {

public static void main(String[] args) {
List<Integer> list1 = Arrays.asList(1, 2, 9, 4, 5);
System.out.println(list1.toString()); // [1, 2, 9, 4, 5]

List<String> list2 = Arrays.asList("abcd", "333", "fdsd", "3332dsdas");
System.out.println(list2.toString()); // [abcd, 333, fdsd, 3332dsdas]

List<B> list3 = Arrays.asList(new B(), new B1(), new B2(), new B3(),
new B4(), new B5());
System.out.println(list3.toString()); // [B@1cfe4b2, B1 , B2 ,
// B3@1f2d08e, B4 , B5@b5c224]

// 数组本身的toString方法未重载，只是简单继承了Object类的toString方法，其返回值是“包名.类名@哈希值”
// 打印数组中的内容，使用的是Arrays。toString方法
Integer[] arr1 = list1.toArray(new Integer[0]);
System.out.println(arr1.toString()); // [Ljava.lang.Integer;@1e25b76
System.out.println(Arrays.toString(arr1)); // [1, 2, 9, 4, 5]

String[] arr2 = list2.toArray(new String[0]);
System.out.println(arr2.toString()); // [Ljava.lang.String;@1a8dfcc
System.out.println(Arrays.toString(arr2)); // [abcd, 333, fdsd,
// 3332dsdas]

B[] arr3 = list3.toArray(new B[0]);
System.out.println(arr3.toString()); // [LB;@a30797
System.out.println(Arrays.toString(arr3)); // [B@1cfe4b2, B1 , B2 ,
// B3@1f2d08e, B4 ,
// B5@b5c224]

double[] arr4 = new double[] { 32, -32.32, -0.99, 43, 66 };
System.out.println(arr4.toString()); // [D@774085
System.out.println(Arrays.toString(arr4)); // [32.0, -32.32, -0.99,
// 43.0, 66.0]

List<Integer> tmpLst = Arrays.asList(6, 40, 1, 3, 4, 5, 3, 1);
Set<Integer> set1 = new HashSet<Integer>(tmpLst); // 自动去重
System.out.println(set1.toString()); // [1, 3, 4, 5, 6, 40]

List<String> tmpList2 = Arrays.asList("abc", "32eds",
new String("abc"), "dsd", "abc", new String("abc"));
Set<String> set2 = new HashSet<String>(tmpList2); // 按内容去重
System.out.println(set2.toString()); // [abc, 32eds, dsd]

B b1 = new B(), b2 = new B(), b3 = b1;
List<B> tmpList3 = Arrays.asList(b1, b2, b3, new B3(), new B4(),
new B());
Set<B> set3 = new HashSet<B>(tmpList3); // 按变量的值去重
System.out.println(set3.toString()); // [B@996db8, B3@1be847c, B4 ,B@2e1f26, B@163006a]

Map<Integer, Double> map1 = new HashMap<Integer, Double>()
{{put(5, 4.345); put(3, 0.3234); put(5, 43.2143); put(0, -99.0);}}; // key值相同，后放入的覆盖之前放入的
System.out.println(map1.toString()); // {0=-99.0, 3=0.3234, 5=43.2143}

Map<String, Integer> map2 = new HashMap<String, Integer>()
{{put("abc", 0); put("123", 0); put("abc", 9); put("1230", 0); put("0123", 8888);}};
System.out.println(map2.toString()); // {abc=9, 123=0, 1230=0, 0123=8888}

Map<B, String> map3 = new HashMap<B, String>()
{{put(new B(), "abc"); put(new B1(), "abc"); put(new B(), "abc"); put(new B2(), "011"); put(new B3(), "::LK"); put(new B4(), ""); put(new B5(), null);
put(null, null);}};
System.out.println(map3.toString()); // {null=null, B@12f65ce5=abc, B2  =011, B@106258e1=abc, B5@41616dd6=null, B4  =, B3@24e5ddd0=::LK, B1  =abc}

}
}

class B {

/*
* @Override public boolean equals(Object obj) { B tmp = (B)obj; if (tmp ==
* this) { return true; } return false; }
*
* @Override public int hashCode() { return super.hashCode();
* //如果hashcode相同，会去执行equals }
*/
}

class B1 extends B {
public String toString() {
return "B1  ";
}
}

class B2 extends B {
public String toString() {
return "B2  ";
}
}

class B3 extends B {
}

class B4 extends B {
public String toString() {
return "B4  ";
}
}

class B5 extends B {
}