list.toArray和 Arrays.asList
2017-04-10 17:34
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public static void main (String args[]){
List<String> list = new ArrayList<>(2);
list.add("one");
list.add("two");
list.add("three");
String[] array = new String[list.size()-1];
array = (String[]) list.toArray(array);
list.set(0, "changeOne");
System.out.println(list.toString());
System.out.println(array.length);
System.out.println(array[0]);
String[] array2 = new String[] {"a", "b", "c"};
List<String> list2 = Arrays.asList(array2);
array2[0]="changeA";
System.out.println(list2.get(0));
}
list转换成array时会新生成一个数组,数据库有两份数据;但是array转换成list就会出现list和array共用一份数据的情况。还有就是array长度就算不够,也会重新生成需要长度的数组;不要使用过大的长度,否则多出长度会为null。
List<String> list = new ArrayList<>(2);
list.add("one");
list.add("two");
list.add("three");
String[] array = new String[list.size()-1];
array = (String[]) list.toArray(array);
list.set(0, "changeOne");
System.out.println(list.toString());
System.out.println(array.length);
System.out.println(array[0]);
String[] array2 = new String[] {"a", "b", "c"};
List<String> list2 = Arrays.asList(array2);
array2[0]="changeA";
System.out.println(list2.get(0));
}
list转换成array时会新生成一个数组,数据库有两份数据;但是array转换成list就会出现list和array共用一份数据的情况。还有就是array长度就算不够,也会重新生成需要长度的数组;不要使用过大的长度,否则多出长度会为null。
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