How can I represent a range in Java?

Question

Let's say an integer should be within the range: [0...2147483647]

I want to check whether an integer variable falls within this range. I know it can be accomplished by a simple if-else statement, but is there a more efficient way to check whether it's within the range?

I'd rather not do this:

if (foo >= 0 && foo <= 2147483647) 
{
    // do something
}

Answer 1

Apache Commons Lang has a Range class for doing arbitrary ranges.

Range<Integer> test = Range.between(1, 3);
System.out.println(test.contains(2));
System.out.println(test.contains(4));

Guava Range has similar API.

If you are just wanting to check if a number fits into a long value or an int value, you could try using it through BigDecimal . There are methods for longValueExact and intValueExact that throw exceptions if the value is too big for those precisions.

Answer 2

You could create a class to represent this

public class Range
{
    private int low;
    private int high;

    public Range(int low, int high){
        this.low = low;
        this.high = high;
    }

    public boolean contains(int number){
        return (number >= low && number <= high);
    }
}

Sample usage:

Range range = new Range(0, 2147483647);

if (range.contains(foo)) {
    //do something
}

Answer 3

I know this is quite an old question, but with Java 8's Streams you can get a range of int s like this:

// gives an IntStream of integers from 0 through Integer.MAX_VALUE
IntStream.rangeClosed(0, Integer.MAX_VALUE); 

Then you can do something like this:

if (IntStream.rangeClosed(0, Integer.MAX_VALUE).matchAny(n -> n == A)) {
    // do something
} else {
    // do something else 
}

Answer 4

You could use java.time.temporal.ValueRange which accepts long and would also work with int :

int a = 2147;

//Use java 8 java.time.temporal.ValueRange. The range defined
//is inclusive of both min and max 
ValueRange range = ValueRange.of(0, 2147483647);

if(range.isValidValue(a)) {
    System.out.println("in range");
}else {
    System.out.println("not in range");
}

Answer 5

如果您要检查很多区间，我建议使用区间树。

Answer 6

You will have an if-check no matter how efficient you try to optimize this not-so-intensive computation :) You can subtract the upper bound from the number and if it's positive you know you are out of range. You can perhaps perform some boolean bit-shift logic to figure it out and you can even use Fermat's theorem if you want (kidding :) But the point is "why" do you need to optimize this comparison? What's the purpose?

Answer 7

For a range of Comparable I use the following :

public class Range<T extends Comparable<T>> {

    /**
     * Include start, end in {@link Range}
     */
    public enum Inclusive {START,END,BOTH,NONE }

    /**
     * {@link Range} start and end values
     */
    private T start, end;
    private Inclusive inclusive;

    /**
     * Create a range with {@link Inclusive#START}
     * @param start
     *<br/> Not null safe
     * @param end
     *<br/> Not null safe
     */
    public Range(T start, T end) {  this(start, end, null); }

    /**
     * @param start
     *<br/> Not null safe
     * @param end
     *<br/> Not null safe
     *@param inclusive
     *<br/>If null {@link Inclusive#START} used
     */
    public Range(T start, T end, Inclusive inclusive) {

        if((start == null) || (end == null)) {
            throw new NullPointerException("Invalid null start / end value");
        }
        setInclusive(inclusive);

        if( isBigger(start, end) ) {
            this.start = end;   this.end   = start;
        }else {
            this.start = start;  this.end   = end;
        }
    }

    /**
     * Convenience method
     */
    public boolean isBigger(T t1, T t2) { return t1.compareTo(t2) > 0; }

    /**
     * Convenience method
     */
    public boolean isSmaller(T t1, T t2) { return t1.compareTo(t2) < 0; }

    /**
     * Check if this {@link Range} contains t
     *@param t
     *<br/>Not null safe
     *@return
     *false for any value of t, if this.start equals this.end
     */
    public boolean contains(T t) { return contains(t, inclusive); }

    /**
     * Check if this {@link Range} contains t
     *@param t
     *<br/>Not null safe
     *@param inclusive
     *<br/>If null {@link Range#inclusive} used
     *@return
     *false for any value of t, if this.start equals this.end
     */
    public boolean contains(T t, Inclusive inclusive) {

        if(t == null) {
            throw new NullPointerException("Invalid null value");
        }

        inclusive = (inclusive == null) ? this.inclusive : inclusive;

        switch (inclusive) {
            case NONE:
                return ( isBigger(t, start) && isSmaller(t, end) );
            case BOTH:
                return ( ! isBigger(start, t)  && ! isBigger(t, end) ) ;
            case START: default:
                return ( ! isBigger(start, t)  &&  isBigger(end, t) ) ;
            case END:
                return ( isBigger(t, start)  &&  ! isBigger(t, end) ) ;
        }
    }

    /**
     * Check if this {@link Range} contains other range
     * @return
     * false for any value of range, if this.start equals this.end
     */
    public boolean contains(Range<T> range) {
        return contains(range.start) && contains(range.end);
    }

    /**
     * Check if this {@link Range} intersects with other range
     * @return
     * false for any value of range, if this.start equals this.end
     */
    public boolean intersects(Range<T> range) {
        return contains(range.start) || contains(range.end);
    }

    /**
    * Get {@link #start}
    */
    public T getStart() { return start; }

    /**
    * Set {@link #start}
    * <br/>Not null safe
    * <br/>If start > end they are switched
    */
    public Range<T> setStart(T start) {

        if(start.compareTo(end)>0) {
            this.start = end;
            this.end  = start;
        }else {
            this.start = start;
        }
        return this;
    }

    /**
    * Get {@link #end}
    */
    public T getEnd() {  return end;  }

    /**
    * Set {@link #end}
    * <br/>Not null safe
    *  <br/>If start > end they are switched
    */
    public  Range<T> setEnd(T end) {

        if(start.compareTo(end)>0) {
            this.end  = start;
            this.start = end;
        }else {
            this.end = end;
        }
        return this;
    }

    /**
    * Get {@link #inclusive}
    */
    public Inclusive getInclusive() { return inclusive; }

    /**
    * Set {@link #inclusive}
    * @param inclusive
    *<br/>If null {@link Inclusive#START} used
    */
    public  Range<T> setInclusive(Inclusive inclusive) {

        this.inclusive = (inclusive == null) ? Inclusive.START : inclusive;
        return this;
    }
}

(This is a somewhat shorted version. The full code is available here )

Answer 8

org.apache.commons.lang.math.NumberRange;

It's a class that extends org.apache.commons.lang.math.Range @pimaster's answer

Answer 9

import java.util.Arrays;

class Soft{
    public static void main(String[] args){
        int[] nums=range(9, 12);
        System.out.println(Arrays.toString(nums));
    }
    static int[] range(int low, int high){
        int[] a=new int[high-low];
        for(int i=0,j=low;i<high-low;i++,j++){
            a[i]=j;
        }
        return a;

    }
}

My code is similar to Python`s range :)

Answer 10

如果您使用 Spring，您可以依赖 org.springframework.data.domain，它非常完整，包括绑定和未绑定范围。