#include <stdio.h>
#include <stdlib.h>
#include <string.h>

typedef char string[100];

void substrings(string str) {
    if (strlen(str) >= 1) {
        puts(str);
        substrings(str + 1);
    }
}

void todas_substrings(string str) {
    int tam = strlen(str);
    if (tam >= 1) {
        substrings(str);
        str[tam - 1] = '';
        todas_substrings(str);
    }
}


int main(int argc, char const *argv[]) {
    string str = "UTFPR";

    todas_substrings(str);

    return 0;
}

UTFPR
TFPR
FPR
PR
R
UTFP
TFP
FP
P
UTF
TF
F
UT
T
U

public class Substring {

    public void todasSubstrings(String str) {
        int tamanho1 = 0;
        int tamanho2 = str.length();

        for(int i = 0; i < str.length(); i++) {
            for(int j = 0; j < str.length(); j++) {
                System.out.println(str.substring(tamanho1,tamanho2));
                tamanho2--;
            }
            tamanho1++;
        }
    }

    public static void main(String[] args) {
        Substring sb = new Substring();

        String str = "UTFPR";

        sb.todasSubstrings(str);
    }
}

Exception in thread "main" java.lang.StringIndexOutOfBoundsException: begin 1, end 0, length 5
        at java.base/java.lang.String.checkBoundsBeginEnd(Unknown Source)
        at java.base/java.lang.String.substring(Unknown Source)
        at Substring.todasSubstrings(Substring.java:10)
        at Substring.main(Substring.java:22)