Java数组技巧攻略

　　　　　　Java数组技巧攻略

0. 声明一个数组（Declare an array）

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1. String[] aArray = new String[5];
2. String[] bArray = {"a","b","c", "d", "e"};
3. String[] cArray = new String[]{"a","b","c","d","e"};

String[] aArray = new String[5];
String[] bArray = {"a","b","c", "d", "e"};
String[] cArray = new String[]{"a","b","c","d","e"};

1. 在Java中输出一个数组（Print an array in Java）

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1. int[] intArray = { 1, 2, 3, 4, 5 };
2. String intArrayString = Arrays.toString(intArray);
3. // print directly will print reference value
4. System.out.println(intArray);
5. // [I@7150bd4d
6. System.out.println(intArrayString);
7. // [1, 2, 3, 4, 5]

int[] intArray = { 1, 2, 3, 4, 5 };
String intArrayString = Arrays.toString(intArray);
 
// print directly will print reference value
System.out.println(intArray);
// [I@7150bd4d
 
System.out.println(intArrayString);
// [1, 2, 3, 4, 5]

2. 从数组中创建数组列表（Create an ArrayList from an array）

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1. String[] stringArray = { "a", "b", "c", "d", "e" };
2. ArrayList<String> arrayList = new ArrayList<String>(Arrays.asList(stringArray));
3. System.out.println(arrayList);
4. // [a, b, c, d, e]

String[] stringArray = { "a", "b", "c", "d", "e" };
ArrayList<String> arrayList = new ArrayList<String>(Arrays.asList(stringArray));
System.out.println(arrayList);
// [a, b, c, d, e]

3. 检查数组中是否包含特定值（Check if an array contains a certain value）

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1. String[] stringArray = { "a", "b", "c", "d", "e" };
2. boolean b = Arrays.asList(stringArray).contains("a");
3. System.out.println(b);
4. // true

String[] stringArray = { "a", "b", "c", "d", "e" };
boolean b = Arrays.asList(stringArray).contains("a");
System.out.println(b);
// true

4. 连接两个数组（ Concatenate two arrays）

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1. int[] intArray = { 1, 2, 3, 4, 5 };
2. int[] intArray2 = { 6, 7, 8, 9, 10 };
3. // Apache Commons Lang library
4. int[] combinedIntArray = ArrayUtils.addAll(intArray, intArray2);

int[] intArray = { 1, 2, 3, 4, 5 };
int[] intArray2 = { 6, 7, 8, 9, 10 };
// Apache Commons Lang library
int[] combinedIntArray = ArrayUtils.addAll(intArray, intArray2);

5. 声明一个数组内链（Declare an array inline ）

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1. method(new String[]{"a", "b", "c", "d", "e"});

method(new String[]{"a", "b", "c", "d", "e"});

6. 将数组元素加入到一个独立的字符串中（Joins the elements of the provided array into a single String）

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1. // containing the provided list of elements
2. // Apache common lang
3. String j = StringUtils.join(new String[] { "a", "b", "c" }, ", ");
4. System.out.println(j);
5. // a, b, c

// containing the provided list of elements
// Apache common lang
String j = StringUtils.join(new String[] { "a", "b", "c" }, ", ");
System.out.println(j);
// a, b, c

7. 将数组列表转换成一个数组 （Covnert an ArrayList to an array）

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1. String[] stringArray = { "a", "b", "c", "d", "e" };
2. ArrayList<String> arrayList = new ArrayList<String>(Arrays.asList(stringArray));
3. String[] stringArr = new String[arrayList.size()];
4. arrayList.toArray(stringArr);
5. for (String s : stringArr)
6. System.out.println(s);

String[] stringArray = { "a", "b", "c", "d", "e" };
ArrayList<String> arrayList = new ArrayList<String>(Arrays.asList(stringArray));
String[] stringArr = new String[arrayList.size()];
arrayList.toArray(stringArr);
for (String s : stringArr)
        System.out.println(s);

8. 将数组转换成一个集合（Convert an array to a set）

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1. Set<String> set = new HashSet<String>(Arrays.asList(stringArray));
2. System.out.println(set);
3. //[d, e, b, c, a]

Set<String> set = new HashSet<String>(Arrays.asList(stringArray));
System.out.println(set);
//[d, e, b, c, a]

9. 反向数组（Reverse an array）

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1. int[] intArray = { 1, 2, 3, 4, 5 };
2. ArrayUtils.reverse(intArray);
3. System.out.println(Arrays.toString(intArray));
4. //[5, 4, 3, 2, 1]

int[] intArray = { 1, 2, 3, 4, 5 };
ArrayUtils.reverse(intArray);
System.out.println(Arrays.toString(intArray));
//[5, 4, 3, 2, 1]

10. 删除数组元素（Remove element of an array）

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1. int[] intArray = { 1, 2, 3, 4, 5 };
2. int[] removed = ArrayUtils.removeElement(intArray, 3);//create a new array
3. System.out.println(Arrays.toString(removed));

int[] intArray = { 1, 2, 3, 4, 5 };
int[] removed = ArrayUtils.removeElement(intArray, 3);//create a new array
System.out.println(Arrays.toString(removed));

One more – convert int to byte array

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1. byte[] bytes = ByteBuffer.allocate(4).putInt(8).array();
2. for (byte t : bytes) {
3. System.out.format("0x%x ", t);
4. }