谷歌团队推荐的Java工具集使用示例2
- 上一篇，Guava Demo1 示例
- 一、List操作
- 1.1 不可变集合ImmutableList
- 1.2 List常见操作
- 1.3 List_Partition操作
- 1.4 Lists_reverse操作
- 二、Set操作
- 2.1 Sets_diff
- 2.2 Sets_intersection
- 2.3 Sets_union
- 三、Optional操作
- 四、Split操作
- 五、Table操作
- 这里是更多关于关于Guava定义的Collections,JDK中没有的
上一篇，Guava Demo1 示例
一、List操作
1.1 不可变集合ImmutableList
public class ImmutableList_ {
public static <T> void iList(List<T> list) {
ImmutableList<T> immutableList = ImmutableList.copyOf(list);
System.out.println(immutableList);
}
public static void iList() {
ImmutableList<String> immutableList = ImmutableList.of("Geeks", "For", "Geeks");
System.out.println(immutableList);
}
@Test
public void t1() {
List<String> list = Lists.newArrayList("Geeks", "For", "Geeks");
iList(list);
iList();
}
@Test
public void t2() {
List<String> list = Lists.newArrayList("Geeks", "For", "Geeks");
ImmutableList<String> iList = ImmutableList.<String>builder()
.addAll(list)
.add("Computer", "Portal")
.build();
System.out.println(iList);
}
@Test
public void t3() {
List<String> list = new ArrayList<>();
list.add("Geeks");
ImmutableList<String> iList = ImmutableList.copyOf(list);
System.out.println(iList);
}
}1.2 List常见操作
public class List_Ope {
private static List<Per> list;
static
{
LocalDateTime now = LocalDateTime.now();
Per p1 = new Per().setPerId(1l).setAge(12).setName("tets").setBirth(now.minusDays(50)).setDeath(now.plusMonths(378));
Per p2 = new Per().setPerId(2l).setAge(28).setName("tets2").setBirth(now.minusDays(25)).setDeath(now.plusMonths(358));
Per p3 = new Per().setPerId(3l).setAge(25).setName("tets3").setBirth(now.minusDays(27)).setDeath(now.plusMonths(338));
Per p4 = new Per().setPerId(4l).setAge(14).setName("tets4").setBirth(now.minusDays(37)).setDeath(now.plusMonths(348));
list = Lists.newArrayList(p1,p2,p3,p4);
}
/**
* 这里只能去除null,无法空串
*/
@Test
public void t1(){
List<String> names = Lists.newArrayList(""," ","John", null, "Adam", null, "Jane","");
Iterables.removeIf(names, Predicates.isNull());
names.forEach(System.out::println);
}
/**
* list过滤
*/
@Test
public void t2(){
List<String> names = Lists.newArrayList("John", "Jane", "Adam", "Tom");
Iterable<String> result = Iterables.filter(names, Predicates.containsPattern("a"));
result.forEach(System.out::println);
}
// 包含"J",或者不包括"a"
@Test
public void t21(){
List<String> names = Lists.newArrayList("John", "Jane", "Adam", "Tom");
Iterable<String> result = Iterables.filter(names, Predicates.or(Predicates.containsPattern("J"), Predicates.not(Predicates.containsPattern("a"))));
result.forEach(System.out::println);
}
//
@Test
public void t3(){
List<Per> pers = Lists.newArrayList(list);
list.forEach(e ->{
if (e.getAge()>15) {
pers.remove(e);
}
});
pers.forEach(System.out::println);
}
// java8 stream 过滤
@Test
public void t4(){
final List<Per> list1 = list.stream().filter(e -> e.getAge() > 20).collect(Collectors.toList());
list1.forEach(System.out::println);
}
// guava 过滤
@Test
public void t5(){
final Iterable<Per> filter = Iterables.filter(list, Predicates.notNull());
filter.forEach(System.out::println);
}
}1.3 List_Partition操作
public class List_Partition {
/**
* 对List切分子List，数字
*/
@Test
public void t1() {
List<Integer> myList = Arrays.asList(1, 2, 3, 4, 5, 6, 7);
List<List<Integer>> lists
= Lists.partition(myList, 2);
for (List<Integer> sublist : lists)
System.out.println(sublist);
}
@Test
public void t2() {
List<Character> myList = Arrays.asList('H', 'E', 'L', 'L', 'O', 'G', 'E', 'E', 'K', 'S');
List<List<Character>> lists
= Lists.partition(myList, 3);
for (List<Character> sublist : lists)
System.out.println(sublist);
}
}1.4 Lists_reverse操作
public class Lists_reverse {
/**
* 逆序输出
*/
@Test
public void t1(){
List<Integer> myList = Arrays.asList(1, 2, 3, 4, 5);
List<Integer> reverse = Lists.reverse(myList);
System.out.println(reverse);
}
}二、Set操作
2.1 Sets_diff
public class Sets_diff {
/**
* 计算两个List差集，注意A，B集合的差集是不同的
*/
@Test
public void t1() {
Set<Integer> set1 = Sets.newHashSet(1, 2, 3, 4, 5, 6);
Set<Integer> set2 = Sets.newHashSet(1, 2, 3, 5, 7);
Set<Integer> diff1 = Sets.difference(set1, set2);
Set<Integer> diff2 = Sets.difference(set2, set1);
System.out.println("Sets.difference(set1, set2):" + diff1); // 4，6
System.out.println("Sets.difference(set2, set1):" + diff2); // 7
}
@Test
public void t2() {
Set<String> set1 = Sets.newHashSet("H", "E", "L", "L", "O", "G");
Set<String> set2 = Sets.newHashSet("L", "I", "K", "E", "G");
Set<String> diff1 = Sets.difference(set1, set2);
Set<String> diff2 = Sets.difference(set2, set1);
System.out.println("Sets.difference(set1, set2):" + diff1); //H，O
System.out.println("Sets.difference(set2, set1)" + diff2); // I，K
}
}2.2 Sets_intersection
public class Sets_intersection {
/**
* Sets取交集，List没有，List里面有重复的元素
*/
@Test
public void t1(){
Set<Integer> set1 = Sets.newHashSet(10, 20, 30, 40, 50);
Set<Integer> set2 = Sets.newHashSet(30, 50, 70, 90);
Set<Integer> answer = Sets.intersection(set1, set2);
System.out.println("Set 1 intersection Set 2: " + answer);
}
@Test
public void t2(){
Set<String> set1 = Sets.newHashSet("G", "e", "e", "k", "s"); // 这里会自动除重
Set<String> set2 = Sets.newHashSet("g", "f", "G", "e");
Set<String> answer = Sets.intersection(set1, set2);
System.out.println("Set 1 intersection Set 2: " + answer);
}
}2.3 Sets_union
public class Sets_union {
@Test
public void t1(){
Set<Integer> set1 = Sets.newHashSet(5,8,3,6,9);
Set<Integer> set2 = Sets.newHashSet(3, 5, 7, 9);
Set<Integer> answer = Sets.union(set1, set2);
Set<Integer> answer2 = Sets.union(set2, set1);
System.out.println("Set 1 : " + set1);
System.out.println("Set 1 union Set 2: " + answer);
System.out.println("Set 2 union Set 1: " + answer2);
}
}三、Optional操作
public class Optional_ {
@Test
public void t1(){
// 初始化 List
List<String> myList = new ArrayList<>();
myList.add("Geeks");
myList.add("for");
myList.add("GeeksClasses");
myList.add(null);
myList.add("GeeksforGeeks");
myList.add("");
myList.add("Data Structures");
displayValuesUsingJavaNulls(myList); // 基础手写方法判断是否为空代码
displayValuesUsingGuavaOptional(myList); // 调用 guava Optional封装方法实现
}
// Method to display values using Java Nulls
public static void displayValuesUsingJavaNulls(List<String> myList) {
System.out.println("Displaying values using Java Nulls");
// For every String in myList
for (String str : myList) {
if (str == null || str.isEmpty()) {
System.out.println("String : Value is empty or not available");
}
else {
System.out.println("String : " + str);
}
}
System.out.println();
}
// 使用 Guava Optional处理
public static void displayValuesUsingGuavaOptional(List<String> myList) {
System.out.println("Displaying values using Guava Optional");
for (String str : myList) {
Optional<String> optionalName = Optional.fromNullable(emptyToNull(str));
System.out.println("String : " + optionalName.or("String : Value is empty or not available"));
}
}
}四、Split操作
public class Split_toList {
/**
* 将string 按照 ','切割成List数组
*/
@Test
public void t1(){
String str = "Hello, geeks, for, geeks, noida";
List<String> myList = Splitter.on(',').splitToList(str);
for (String temp : myList) {
System.out.println(temp);
}
}
/**
* 不可以连续切，只匹配后面的 on()
*/
@Test
public void t2(){
String str = "Everyone. should. Learn, Data. Structures";
List<String> myList = Splitter.on('.').on(',').splitToList(str);
for (String temp : myList) {
System.out.println(temp);
}
}
/**
* 对分割符前后的空格或者为空时的处理
*/
@Test
public void t3(){
String str = " , Everyon , , should, Learn, Data, Structures";
List<String> guaList = Splitter.on(',').trimResults().omitEmptyStrings().splitToList(str);
for (String temp : guaList) {
System.out.println(temp);
}
}
}五、Table操作
public class Table_ {
@Test
public void t1(){
Table<String, String, String> studentTable = HashBasedTable.create();
studentTable.put("CSE", "5", "Dhiman");
studentTable.put("CSE", "7", "Shubham");
studentTable.put("CSE", "9", "Abhishek");
studentTable.put("CSE", "12", "Sahil");
studentTable.put("ECE", "15", "Ram");
studentTable.put("ECE", "18", "Anmol");
studentTable.put("ECE", "20", "Akhil");
studentTable.put("ECE", "25", "Amrit");
Map<String, String> eceMap = studentTable.row("ECE");
System.out.println("List of ECE students : ");
for (Map.Entry<String, String> student : eceMap.entrySet()) {
System.out.println("Student Roll No : " + student.getKey() + ", Student Name : " + student.getValue());
}
System.out.println();
Map<String, String> stuMap = studentTable.column("12");
for (Map.Entry<String, String> student : stuMap.entrySet()) {
System.out.println("Student Roll No : " + student.getKey() + ", Student Name : " + student.getValue());
}
}
}这里是更多关于关于Guava定义的Collections,JDK中没有的
