1.构造Range实例必须使用Range中的静态方法,因为Range的构造方法被设置为private,当a > b使,或者当a == b且为(a,b)时会抛出IllegalArgumentException
(a,b) | Range.open(a, b) |
(a, b] | Range.openClosed(a, b) |
[a, b] | Range.Closed(a, b) |
[a, b) | Range.closedOpen(a, b) |
[a, +∞) | Range.atLeast(a) |
(a, +∞) | Range.greatThan(a) |
(-∞, b] | Range.atMost(b) |
(-∞, b) | Range.lessThan(b) |
(-∞, +∞) | Range.all() |
2. Range的一些常用方法
<1>. contains()方法用来判断区间是否包含一个给定的值
Range.closed(
1
,
3
).contains(
2
);
//return true
Range.closed(1, 3).contains(4);//return false
<2>.hasLowerBound()方法和hasUpperBound()方法是用来判断边界是否为无穷
Range.greaterThan(3).hasLowerBound() //return true
Range.greaterThan(3).hasUpperBound() //return false
Range.lessThan(3).hasLowerBound() //return false
Range.lessThan(3).hasUpperBound() //return true
<3>.lowerBoundType()方法和upperBoundType()方法用来返回边界类型(OPEN, CLOSED),
若边界是无穷,则抛出 IllegalStateException
<4>.lowerEndpoint()和upperEndpoint():返回区间的端点值;如果区间的端点值为无穷,抛出 IllegalStateException
<5>.isconnect()判断连个区间是否能连在一起
<6>.intersection(Range)返回两个区间的交集:既包含于第一个区间,又包含于另一个区间的最大区间。当且仅当两个区间是相连的,它们才有交集。如果两个区间没有交集,该方法将抛出IllegalArgumentException。
<7>.span(Range)返回”同时包括两个区间的最小区间”
- 示例
import com.google.common.collect.ContiguousSet;
import com.google.common.collect.DiscreteDomain;
import com.google.common.collect.Range;
import com.google.common.primitives.Ints;
public class GuavaTester {
public static void main(String args[]){
GuavaTester tester = new GuavaTester();
tester.testRange();
}
private void testRange(){
//create a range [a,b] = { x | a <= x <= b}
Range<Integer> range1 = Range.closed(0, 9);
System.out.print("[0,9] : ");
printRange(range1);
System.out.println("5 is present: " + range1.contains(5));
System.out.println("(1,2,3) is present: " + range1.containsAll(Ints.asList(1, 2, 3)));
System.out.println("Lower Bound: " + range1.lowerEndpoint());
System.out.println("Upper Bound: " + range1.upperEndpoint());
//create a range (a,b) = { x | a < x < b}
Range<Integer> range2 = Range.open(0, 9);
System.out.print("(0,9) : ");
printRange(range2);
//create a range (a,b] = { x | a < x <= b}
Range<Integer> range3 = Range.openClosed(0, 9);
System.out.print("(0,9] : ");
printRange(range3);
//create a range [a,b) = { x | a <= x < b}
Range<Integer> range4 = Range.closedOpen(0, 9);
System.out.print("[0,9) : ");
printRange(range4);
//create an open ended range (9, infinity
Range<Integer> range5 = Range.greaterThan(9);
System.out.println("(9,infinity) : ");
System.out.println("Lower Bound: " + range5.lowerEndpoint());
System.out.println("Upper Bound present: " + range5.hasUpperBound());
Range<Integer> range6 = Range.closed(3, 5);
printRange(range6);
//check a subrange [3,5] in [0,9]
System.out.println("[0,9] encloses [3,5]:" + range1.encloses(range6));
Range<Integer> range7 = Range.closed(9, 20);
printRange(range7);
//check ranges to be connected
System.out.println("[0,9] is connected [9,20]:" + range1.isConnected(range7));
Range<Integer> range8 = Range.closed(5, 15);
//intersection
printRange(range1.intersection(range8));
//span
printRange(range1.span(range8));
}
private void printRange(Range<Integer> range){
System.out.print("[ ");
for(int grade : ContiguousSet.create(range, DiscreteDomain.integers())) {
System.out.print(grade +" ");
}
System.out.println("]");
}
}